Angel's story before he met Buffy unfolds in flashbacks scattered among numerous episodes of both Buffy the Vampire Slayer and Angel, presented out of chronological order.

Born in 1727, Liam (no surname given) was born to a middle-class linen merchant in Galway, Ireland. By 1753, at the age of 26, he develops a taste for alcohol, women and sloth. Liam is a hedonist whose only real ambition lies in seeing the world. For a drunken layabout, this seems a laughable dream, until he is expelled from his house by his disapproving father. While engaging a drunken tavern brawl that evening, he catches the eye of Darla, a vampire disguised as a noblewoman. Upon being tossed out of the tavern for causing trouble, Liam is lured into an alley by Darla, who promises to show him the world, then transforms him into a vampire. The price is the loss of his human soul, along with his conscience, freeing Liam to act upon his darker impulses.

On the night he rises from his grave, Liam sets about murdering the entire community, culminating in an attack on his own house. He first kills his little sister, Kathy, who unknowingly invited the demon in, believing that Liam had come back to her as an "angel", subsequently killing his parents. Kathy's belief that he was an angel was likely the inspiration for his vampire name, "Angelus" (the Latinate for "Angel"). He is later described in historical volumes as "the demon with the face of an angel" ("Somnambulist"). After leaving Ireland, Angelus and Darla cut a bloody swath through Wales and northern England, before finally reaching London in 1760. During Angelus's first meeting with the Master in the city sewers, he openly mocks the older vampire despite the power and authority, showing no fear despite the Master's greater age, and confronts Darla about her decision to remain underground when she could be traveling the world with him. Won over by his words, Darla chooses to live with Angelus, abandoning the Master's leadership.

In May 1764, Angelus and Darla killed the family of vampire hunter Daniel Holtz. Holtz devoted himself to capturing Angelus and Darla, chasing them across Europe. Angelus and Darla had a near miss in France, after making too much noise by ordering room service and eating the waiters. Darla flees to Austria, leaving Angelus in a burning barn and riding off on their only horse. After meeting again in Vienna, Angelus and Darla sire the vampires James and Elizabeth. In Marseilles, 1767, Holtz tracks them down and manages to put numerous arrows in Angelus. Holtz briefly lost them in northern Africa, only to track Angelus to Rome, Italy in 1771. Instead of killing Holtz, Angelus and Darla realize that they have come to view him "like family" and make a sport of ruining his life. Holtz abandons his hunt and retires to York, England, until in 1773 a demon named Sahjhan offers to take him to the future where he may continue his revenge.

Angelus later sires a Puritan by the name of Penn, who mimics Angelus by wreaking havoc on his father and killing his family. Over time he begins copying Angelus' 'signature' of leaving a cross-shaped mark on the face of his victims in order to spite God. In 1789, Angelus- apparently alone for reasons unknown- encounters The Beast in Prussia, standing in a field of bodies, who seeks Angelus's aid in killing the Svear Priestesses, a group who wish to banish the Beast and who can only be killed by a vampire. When he declines to join with the Beast, he is met with violent reprisal, but a group of Svear priestesses banish the Beast while Angelus is passing out.

In 1860, Drusilla from London, England, a young woman "cursed" with the "sight," something her mother saw as "an affront to the Lord," catches the attention of Angelus. Drusilla and her sisters are all noted to be virgins, and Drusilla is described as having been "sweet, pure and chaste." While posing as her priest to torment her, Angelus killed her family, which caused Drusilla to flee to a convent. On the day she was to take her holy orders, Angelus massacred the convent (he had an obsession with nuns, including a massacre of those at "Our Lady of Lochenbee"). After having sex with Darla right in front of Drusilla, Angelus finally pushed her over the edge, driving her insane before he finally sired her. Drusilla is Angelus' "masterpiece," an everlasting example of his finest cruelty, as her immortality means that her torment shall never end.

Drusilla, in turn, sires William the Bloody, for whom Angelus largely served as a mentor and "role model." William, who later becomes known as "Spike," goes so far as to call the elder vampire his "Yoda". Angelus taught William about the art of mass slaughter, including an incident during a wedding party where Angelus beat the groom to death with his own arm. Angelus threatens to stake Spike in a London mine shaft in 1880, as punishment for putting the vampire quartet on the run after attracting too much attention. Angelus introduces Spike to the existence of the Slayer as a cautionary tale, but Spike takes it as a challenge.

In 1890, Angelus attended a production of Giselle by the Blinnikov, a Russian ballet troupe run by Count Kurskov. Despite being evil, he is moved to tears during the performance (Angel refers to this incident in an episode, saying that he "cried like a baby, and I was evil!"). In 1894, Angelus and Spike are captured by the Immortal's henchmen in Rome, Italy and hung from a ceiling while the Immortal had a threesome with Darla and Drusilla. After the henchman free them with little explanation, the vampire duo are enraged when their respective consorts wax about the Immortal's actions. Both vow vengeance against the Immortal, but don't get close to him again until 2004, in the midst of a case for Angel Investigations. Darla and Angelus were also present at an earthquake in Budapest, Hungary around the turn of the century, where Angelus was a particularly "bad boy."

Cursed

In 1898, while in Borşa, Romania, Angelus tortured and murdered the favorite daughter of a tribe of Kalderash Gypsies, apparently a birthday present from Darla. To avenge her death, the Kalderash gypsies curse him by restoring his human soul, thus afflicting him with a conscience and condemning him to an eternity of remorse for the crimes he has committed. Darla finds Angel huddling in their apartment muttering about all the atrocities they have committed. Repulsed by his "filthy human soul," Darla tries to coerce the father of the dead Gypsy girl to reverse the curse; an overeager Spike kills the rest of the tribe while Darla is busy negotiating with the man. Seeing her leverage has been wasted, a frustrated Darla snaps the father's neck and leaves. Angelus is left homeless and scavenging the streets for rats. He attempts to kill a woman, but finds that he cannot bring himself to do so.

During the Boxer Rebellion in Beijing, China, the ensouled vampire, now known as "Angel," tries and fails to resume his life with Darla. To satisfy her, he starts killing humans again, but Darla notices that he is only hunting rapists and murderers, never targeting innocents. Darla catches Angel trying to hide a group of Christian missionaries from her. When Angel goes to feed on rats down at the waterfront, Darla kills the missionary family and brings back their infant child as a test for Angel. Unable to kill it, Angel flees with the baby and separates from Darla for good, stating that he can't continue to be something he's not.

Angel arrives in New York City, New York through Ellis Island in 1902. Some time later, during the Great Depression, he traveled through Montana. During World War II, Angel is coerced by The Demon Research Initiative into undertaking a secret mission: He must rescue an American submarine crew from three vampires (including Spike) who were captured by the Nazis as part of an experiment to create super-soldiers. During the mission, Angel is forced to sire a fatally-injured Sam Lawson in order for him to repair the submarine's engine, which was damaged during a German attack. Angel later claims to have known Bugsy Siegel around this time, in the early days of Las Vegas, Nevada.

In 1952, while in Los Angeles, California, Angel was a resident at the Hyperion Hotel, the future base of Angel Investigations. Although he tried to isolate himself, Angel was sought out by Judy, who had fled her home town after stealing a sum of money from her job when it was revealed that she had a black mother and a white father. Things quickly deteriorate when a string of murders and suicides gripped the hotel, and the guests become increasingly paranoid. As Angel learns, this is the result of a Thesulac demon, a demon living off fear. Although he initially tried to kill the demon, the guests at the hotel turn against him, and Angel is lynched. Surviving the hanging, and disgusted with the humans, Angel freely allows the demon to consume everyone inside the hotel.

Angel claims to have known the Rat Pack and to have been present during Elvis Presley's wedding reception after his marriage to Priscilla Ann Beaulieu in Las Vegas, Nevada on May 1, 1967.

In New York during the 1970s, Angel witnesses a robbery at a doughnut shop.[2] After the robber shoots an employee and runs away, Angel stays with the man as he dies, and then proceeds to feed on him. Disgusted with himself, Angel then exiles himself to the alleyways, where he spends another 20 years homeless and feeding on rats.

Two decades later, a shadow of his former self, the reclusive Angel is sought out by a demon named Whistler in 1996. Whistler persuades Angel to join the fight against evil. He then brings Angel to meet the newly-called Vampire Slayer, Buffy Summers in Los Angeles. The following year, when he and Buffy finally meet in Sunnydale, he introduces himself, not as Angelus, but as Angel.

Sunnydale

Although Angel already sees Buffy while she is still in L.A., he does not introduce himself to her until after her move to Sunnydale, and after her first day at Sunnydale High.[4] The two fall in love, but Buffy does not realize Angel is a vampire until several weeks later in the episode "Angel", when he unintentionally vamps out after kissing her. Though they try to deny their feelings, they cannot resist the passion growing between them, and the two begin to date after Angel helps to save her from a demonic frat party. When they finally consummate their relationship in "Surprise", Angel experiences one moment of pure happiness, which breaks the Gypsy curse, and loses his soul. Without the compassion and conscience instilled by his human soul, Angel instantly reverts to his former evil self, Angelus, in the following episode.

Angelus allies himself once again with Spike and Drusilla, who have recently settled in Sunnydale. Resenting the humiliation he felt because Buffy had made Angel feel like a human being, Angelus takes immense pleasure in tormenting the Slayer and her friends. First, he helps Spike and Dru deploy a powerful demon known as the Judge. After Buffy destroys the Judge, Angelus embarks on a guerilla campaign, lurking in the shadows, preying on Buffy's classmates, sending her gruesome messages, even drawing pictures of her and her mother as they sleep and leaving them in her bedroom.

He proceeds to murder Jenny Calendar, which serves him in two ways; First, he eliminates an enemy (Jenny was born Janna of the Kalderash clan) and destroys her work just as she manages to successfully decipher the lost Gypsy curse which could be used to restore Angel's soul. Second, Angelus uses Jenny's death to viciously torment Rupert Giles, Jenny's paramour and the person on whom Buffy depends most. After this, Angelus widens his focus and begins a scheme to awaken the demon Acathla and bring about the end of the world. Buffy is determined to stop him despite their history, and is able to overcome him in combat. Just as she prepares for the finishing blow however, Willow Rosenberg is able to restore Angel's soul. Since Acathla can only be stopped by the blood of the individual who activated him, Buffy is forced to sacrifice Angel to save the world. Impaled on the Slayer's enchanted sword, Angel is sucked into Acathla's vortex which suddenly snaps closed.[6]

Angel returns to Earth in "Faith, Hope & Trick". Because time moves differently in Acathla's dimension, he has experienced several hundred years of torment, and when he reappears in his mansion, he is in a feral state. Buffy finds him and helps restore him to sanity, but he begins to suspect that whatever force returned him from his Hell has a purpose of its own. He begins to experience what he believes to be hallucinations of his many past victims, most notably Jenny Calendar, taunting him to kill Buffy. He discovers that the First Evil is not only apparently responsible for his return to Earth, but is responsible for the "hallucinations" (The First has the ability to take the form of anyone who has died, and to make itself visible only to whom it wishes). He resists, choosing instead to commit suicide by staying outside when the sun rises, but a sudden, unexplained snow clouds the Sun.

Angel and Buffy attempt to resume their relationship, but Angel begins to doubt that he will ever be able to give Buffy a remotely human life. When Buffy's mother and even the season's "Big Bad," Mayor Richard Wilkins, tell him that he cannot give her a real future, he tells Buffy that he is leaving Sunnydale after they stop Wilkins, although they share a last dance at her prom. In an attempt to distract Buffy, rogue slayer Faith Lehane shoots him with an arrow coated with poison that can only be cured with the blood of a Slayer. When Buffy is unable to bring him the body of Faith, she tells him to drink from her. He is cured, but nearly kills her in the process when he gives in to his instincts, although he manages to get her to the hospital in time to save her life. He tells Buffy that he's just going to leave without saying goodbye; when they win the fight against Wilkins, Angel and Buffy share a look, and then he leaves for Los Angeles.

Angel Investigations

In L.A., Angel spends a few months alone, patrolling dives and dark alleys, battling vampires who hunt there. Soon enough, he receives support in his attempts to redeem himself in the service of others. First, Doyle, a half-demon and fellow Irishman, is sent by The Powers That Be. Almost immediately thereafter, Angel runs into Cordelia Chase, a former classmate of Buffy's who has moved to L.A. to find wealth and fame. The trio form Angel Investigations, a shoestring operation whose mission statement is to "Help the Helpless."

Doyle, Angel's trusted friend and sole connection to the Powers, sacrifices himself in the episode "Hero" to save others, leading Angel to become even more protective of those few he holds dear. Wesley Wyndam-Pryce, who had briefly served as Watcher to both Buffy and Faith in Sunnydale, arrives in L.A. claiming to be a "rogue demon hunter," a lone wolf sort who only works solo. After their first case, however, Wesley is eager to stay and assist Angel and Cordelia in their mission. A few months later, they are joined by lifelong demon fighter, Charles Gunn. During this time, three young Wolfram and Hart associates, Lindsey McDonald, Lee Mercer, and Lilah Morgan, attempt to have Angel killed by the rogue vampire slayer, Faith. Under Angel's influence, the deeply troubled Faith starts along her own path to redemption, ultimately turning herself in to the police as the first step toward making amends for her crimes.

As Angel continues to help the helpless in Los Angeles, his good deeds begin to seriously disrupt the plans of the evil inter-dimensional law firm, Wolfram and Hart. In an attempt to control him, the firm resurrects his sire and former lover, Darla, who comes back as a human rather than as a vampire. Wolfram and Hart then summons Drusilla, who turns Darla into a vampire again. Angel turns to a darker side of himself, fires his crew, and embarks on a vendetta against both the law firm and the newly reunited Darla and Drusilla. During this time, Angel refuses to prevent the slaughter of a very large group of Wolfram & Hart employees at the hands of Dru and Darla, although he later aids the Host in averting the end of the world when an attempt to stop time goes wrong. After a devastating spiritual defeat by Holland Manners, who tells him that the evil of Wolfram & Hart simply comes from humanity rather than demons, Angel attempts to shed his soul by having sex with Darla, but instead of happiness, finds despair.A moment of clarity follows the desperate act, and Angel realizes that his purpose is still to do all the good he can, even if he can't do all the good he wants, because, in a world where there's no grand final plan, a single act of kindness can make all the difference in the world.

Having hoped to get her boy Angelus back, Darla is horrified and infuriated by Angel's epiphany, and flees Los Angeles. After a difficult reconciliation that involves Wesley taking over the official position of leader of the group, the Angel Investigations team find themselves transported to the demon dimension, Pylea in the episode "Over the Rainbow" when an attempt to vanquish a demon goes wrong and results in Cordelia being sent into the other dimension. Eventually, after Angel defeats the undefeated Champion of Pylea, the Groosalugg, they return with a new team member, Winifred Burkle, in tow, and to the news that the love of Angel's life, Buffy, has died. During this time the Angel Investigations team also enlists the help of demon karaoke bar-owner Lorne, known initially only as The Host.

Fatherhood

Despite Buffy's miraculous resurrection a few months later, Angel finds that his previously platonic love for Cordelia has grown to be romantic. Before he has a chance to confess his feelings, however, Darla returns, pregnant with his son, to be named Connor. False prophecies, time travelers and betrayal lead to Angel losing his infant son to an old enemy, Holtz, who abducts Connor soon after his birth, taking him to a hell dimension (Quor-Toth) where time passes differently. When Connor returns days later, he is a young man who has been raised by Holtz to believe that Angel is still a soulless monster. Holtz takes his own life in such a way that Connor is led to believe he was killed by Angel, and vows to make Angel pay for the suffering he had caused Holtz. That same night, Connor sinks his father to the bottom of the ocean in a steel coffin and Cordelia ascends to a higher plane, the feelings shared between her and Angel still left unspoken.

Rescued by Wesley from his watery prison three months later, Angel's relationship with Connor is strained. It is complicated further by the return of an amnesiac Cordelia, who prefers to stay with Connor because he told her the truth while the others lied to her (albeit because they thought it was for her own good). When a very powerful demon known only as the Beast arrives and begins an attempt to bring forth an apocalypse, Angel's worst fears are realized when he has to strip himself of his soul and revert to his evil alter ego in order to defeat it. Angelus does indeed overcome the Beast, and is also deft enough to realize that the Beast was a mere "flunkie" serving an even deeper evil; the Beast he knew was only interested in smashing and slaughter, and it was unlikely that the Beast would have become smarter since Angelus fought him.

Although he is momentarily free to wreak a little havoc of his own, Angelus is recaptured and re-ensouled with the help of Faith (who almost dies in her quest to capture Angelus) and Willow, culminating in a brief but violent mental battle between Angel and Angelus. After his soul is restored, Angel figures out that the enemy he has been battling is a little closer to home than the group had previously considered, realizing that whatever the Beast's "boss" is, it is using Cordelia's body to carry out its plans. After battling and defeating the divine being known as Jasmine, Angel is offered the L.A. branch of Wolfram & Hart on the grounds that he ended world peace. Angel acts against all of his instincts and makes a deal with his sworn enemy, in exchange for Wolfram & Hart erasing Connor’s memories and giving him a normal life, and trying to find a way to cure Cordelia, who fell into a coma after Jasmine was born.

Wolfram & Hart

The lines between good and evil blur as Angel moves into Wolfram & Hart, and they challenge Angel's perceptions of himself and his destiny. Matters are further complicated when Spike appears as a ghost, emerging from a familiar amulet sent to Angel in the mail. Sharing a complicated history of murder and mayhem, they have spent more than a century as rivals in everything. Now both possessing souls, and both still in love with Buffy, they have evolved into very different heroes in the war against evil. Forced to co-exist, they wage a protracted, insidious battle of wits, ending when they finally come to an understanding and acceptance of their unique brotherhood on their journey to redemption.

In the episode "Destiny," when they prepare to do battle over the Cup of Perpetual Torment, Spike tells Angel "You had a soul forced on you. As a curse. Make you suffer for all the horrible things you've done. Me, I fought for my soul, went through the demon trials, almost did me in a dozen times over, but I kept fighting. Because I knew it was the right thing to do. It's my destiny." Although the Cup turns out to be fake, Angel's defeat at the hands of Spike is a source for inner turmoil in the following episodes, as he left wondering if he is still the vampire champion of the prophecy. Most of these events turn out to be the machinations of Lindsey McDonald, a returning nemesis, and after he is defeated, Angel grows more confident once more.

This defeat coincides with a last visit from Cordelia, who passes along a single vision to Angel. Now finally understanding that he will never be able to completely stop the forces of evil, Angel decides that temporarily severing the Senior Partners' hold on Earth is enough. Together with his comrades, Angel prepares to suicidally incur the apocalyptic wrath of the Senior Partners as a way of going out in a blaze of glory. They assassinate the members of the Circle of the Black Thorn, the Senior Partners' instruments on Earth for pulling all the political and economic strings. In this effort, Gunn is badly wounded, and Wesley Wyndam-Pryce is killed. Lorne is instructed to kill Lindsey, temporarily an ally, after they've completed their mission, and he does so, leaving behind Angel and his team afterwards. Gunn manages to make it to the meeting point, the alley behind the Hyperion Hotel, where he, Angel, Spike and Illyria engage in battle with the dark armies that the Senior Partners have sent against them. The last words spoken on screen are Angel's, "Let's go to work."

Source: http://en.wikipedia.org/wiki/Angel_(Buffyverse)