Angel leaves Sunnydale for Los Angeles, where he meets Doyle, a spiritual mentor who has visions of those in need. Doyle tells him he must get involved with people again, and tells him of a waitress who needs help. She and Angel go to a Hollywood party, where he meets Cordelia, now a struggling actress. But this first assignment goes wrong when the woman he is supposed to help dies at the teeth of a vampire. Then Cordelia is abducted. Angel rescues her, then confronts the vampire in his office, and pushes him out of the window. (In LA, Angel seems to be able to cope with sunlight provided its not direct.) Angel then phones Buffy, but hangs up without saying anything when she answers. He, Cordelia, and Doyle join forces.
Doyle gets a vision of a bar, but no specific person. Cordelia gets some business cards made. Angel meets up with a lonely woman, but misses the demon. But that woman is an undercover cop, Kate Lockley, and mistakes Angel for the killer. He escapes, and continues to track the demon down. It preys on lonely people, and takes over their bodies, leaving the old one as a husk. Angel and the cop finally track it down after it takes the form of the barkeeper.
Buffy sends Angel a magic ring that makes him invulnerable. Angel hides it in the sewers. But Spike has followed [the opening scene, where he provides alternative dialogue for a conversation between Angel and a woman he is helping, is priceless], and captures Angel, handing him over to a vampire torturer in order to find the ring. Cordelia and Doyle find the ring, and use it to rescue Angel. The torturer takes the ring, and is just about to start a daylight reign of terror when Angel jumps him. They fight under a pier, and Angel takes the ring from him. Angel enjoys his first sunshine and sunset in hundreds of years, then decides to destroy the ring, because the little people of the night need him more. [Personally, I think a better reason to destroy it was that it was too powerful, and dreadfully easy to steal, given that Harmony, Spike, Angel, and the torturer, had all had it, and had it stolen from them, in short order.]
Melissa Burns is being stalked by her obsessive neurologist, Ronald Meltzer. He has psychic surgeon abilities to detach parts of his body: an eye to spy on Melissa, hands to strangle a cop. Angel confronts him, and in the final showdown, the doctor falls to pieces.
Cordelia, grossed out by the cockroaches in her flat, in desperation turns to Doyle for help in finding her a new one. He comes up with what looks like a dream apartment too good to be true. It is -- it's haunted by a ghost who kills any female occupant, making the death look like suicide. And Doyle has his own problems -- a debt-collecting demon wants to kill him. Cordelia refuses to give up the perfect apartment, and narrowly escapes being hanged. She fights back against the ghost, who is a mother who bricked up her wayward son, then died of a heat-attack. Knocking down the wall reveals the skeleton, and his ghost drives away his mother's. Cordelia can live with the new, benign, ghost.
Kate Lockley attacks a suspect. She asks Angel to help her find a crime boss. He succeeds, but has to get involved in the arrest. Kate and other cops are sent on "Sensitivity Training" -- but the "Talking Stick" is cursed. All the cops start behaving hyper-sensitively -- Kate breaks down at her father's retirement party, another cop claims he loves her, and one cop lets out all the arrested suspects, including the crime boss. Angel realises there is a sensitivity problem, and confronts the counsellor -- who is in the pay of the spooky law-firm Wolfram and Hart, and involved with several demons. He tries to turn Angel "How were your parents?" "My parents were fine. Tasted like chicken." Angel defeats him, but gets contaminated by the stick. There's a shoot-out at the police station, but the crime boss is defeated. Wolfram and Hart refuse to help him any more, saying they have a bigger problem -- Angel.
When Doyle saves Cordelia from a vampire, she starts to think better of him. But then his estranged wife visits, asking for a divorce, so that she can marry into a restaurant-owing demon family. Doyle is distraught; he had always thought she had left him because she found out he was half demon. But he signs the divorce papers, and gives the demon his blessing, unaware that the family intend to "eat the brain of the first husband" at the stag night. Angel saves the day, and Cordelia still doesn't know Doyle's secret. Right at the end, Doyle has a vision of Buffy in trouble.
Buffy comes to ask Angel why he came to Sunnydale and didn't speak to her. As they talk, they are attacked by a demon assassin. It escapes and they chase it together. Angel finally kills it, gets some of its blood in a cut, and becomes mortal. He checks with the Oracles that this is permanent -- it is. So he and Buffy have an ecstatic reunion. Then Doyle discovers the demon isn't really dead, and he and Angel go to fight it without Buffy. But Angel is too weak to fight it now he is mortal, and gets severely trounced. The demon taunts Angel that there will soon be another thousand warriors like him. Buffy discovers from Cordelia where Angel has gone, and arrives in the nick of time. She can't quite kill it alone, but Angel works out from something Doyle had said they need to break the jewel in its head. Angel discovers that Buffy will die soon, fighting the thousand demons alone, so asks the Oracles to restore him. The only way they can do that is to turn back the clock by 24 hours -- with only Angel remembering what happened.
A clan of half-demons is targetted for extermination by the Scourge: a gang pure-blood demons [the Nazi symbolism could hardly been less subtle]. We learn what Doyle needs to atone for: he once refused to help some half-demons escape the Scourge, and his first ever vision was seeing that they all died. Angel offers to help these demons by finding them safe passage away on a ship. Cordelia discovers at last that Doyle is half-demon, and is totally unfazed by the revelation. Angel infiltrates the Scourge to discover their plans: they have a magic light source that will kill anyone with human blood, and plan to load it onto the ship. They do, but in the last fight, Doyle sacrifices himself to destroy the light.
Angel goes to the Oracles and asks them to turn back time to restore Doyle. They refuse; that would deny his sacrifice. Cordelia discovers that Doyle's kiss transferred his connection to the PTB to her when she has a vision of a "grey blob". A demon comes to Angel for help -- he's being pursued by a dangerous demon hunter -- who turns out to be Wesley! Angel discovers there is another demon, who is much more dangerous, and he and Wesley track it down. But when they find it, they discover the original demon was in fact the evil one, a power stealer -- and he has now captured Cordelia, and is auctioning her seer's eyes to the highest bidder. Angel realises her "blob" vision was of a piece of modern art, and tracks down the hotel exhibiting it. He and Wesley arrive just in the nick of time to save Cordelia, who is disgusted at how low the bidding started.
Several murder victims are found with crosses cut into their faces and bite marks on their necks. Angel is worried he might be doing this in his sleep, because he is dreaming their deaths, and this is how he killed people in the past. But then he realises the culprit is a vampire he sired and taught to kill like this. In the process of taking down the killer, Kate discovers Angel is a vampire.
Cordelia has a one-night stand with a famous but sensitive photographer, and wakes up eight-and-a-half months pregnant. Angel tracks down the friend who introduced them, and discovers she is also pregnant. The photographer is one of a group who are working for a demon, impregnating women with his seed in return for successful careers. This demon is virtually indestructible, and big , but Angel and Wesley must kill it before the births, which the mothers would not survive.
Angel and a female demon reluctantly team up to rescue others of her kind who are being persecuted and enslaved by the male demons. A lot of ice is involved.
Cordelia has a vision of a family where someone is possessed by a demon. Angel tricks his way into the household, and exposes the demon possessing the little boy. The family agree to an exorcism, but the demon escapes, rather than being killed. When Angel and Wesley track down the escaped demon, it tells them that the little boy is a conscienceless monster it had been trying to control and escape from. Angel rushes back to the house, barely in time to save the family from being set on fire by the boy.
We see flashbacks of Angel's bad relationship with his father, which helped make him into a dissolute youth, ripe for being seduced by a vampire. Meanwhile he helps Kate, still ambivalent about her reaction to knowing he's a vampire, track down a drug dealing demon. But Kate's own father is mixed up in the dealing.
Angel is captured by the owners of a "fight club", and forced to fight for his life against other gladiator-demons, for sport, chained in place by a magic cuff. A mysterious lawyer from Wolfram & Hart offers him freedom, but he refuses to pay her asking price: to forget what is happening to the other fighters. Wesley and Cordelia track him down, and discover how to open the cuff.
Rebecca, an actress at a low point in her career, is being menaced by a stalker. Angel saves her life, and in the process accidentally reveals himself to be a vampire. But she's not afraid of him. He becomes her bodyguard, and caches the stalker -- who is revealed to be a plant by her manager trying to get publicity. She decided she wants to keep her looks forever, by getting Angel to make her into a vampire, so drugs him to "relax" him. But the drug gives him synthetic "perfect happiness", and he reverts to Angelus, terrifying Rebecca, and nearly killing Wesley and Cordelia. They manage to restrain him until the drug wears off, and he becomes Angel again.
Angel persuades Marquez to testify against a gang of drug dealers, which annoys their lawyers, the sinister firm Wolfram and Hart. So they hire bad girl Faith the Vampire Slayer, newly arrived in LA, to kill him. She plays with him, attacks Cordelia, and tortures Wesley, before he'll fight her. But it's all bravado, and when they fight, she breaks down and begs him to kill her.
Angel tries to help Faith to mend her ways. But she is pursued by Kate Lockley, the Watcher Council, and Buffy. Wolfram and Hart set a demon assassin on Angel, but Faith kills it. Eventually Faith gives herself up to the police.
Angel helps a billionaire trying to recover compromising photographs taken in a demonic brothel. In the process he finds a group of street kids defending themselves against a nest of vampires. The kids nearly kill him, and are very suspicious of his offers of help.
Angel witnesses a blind assassin at work, but Wolfram and Hart get her off, and Angel is frustrated by his helplessness. Then Lindsey, a W&H lawyer, discovers that the assassin's next task is to kill three children, and discovers he cannot stomach this. So he joins forces with Angel to stop the killings. With the insider's help, Angel steals encrypted data discs and a mysterious scroll from the W&H vaults, and Wesley discovers the children are seers. Cordelia decrypts the discs, with a little phone help from Willow. Angel beats the assassin and saves the children. But in the end, W&H lure Lindsey back into the fold.
Wesley tries to translate the prophesies of Aberijan -- they seem to be about Angel's death. The lawyers from Wolfram and Hart raise the demon Vocah, who drives Cordelia mad with her visions, kills the Oracles, steals the scroll back from Angel, and blows up Wesley. Angel, after snarling at a hostile Kate Lockley, manages to steal the scroll back, and Wesley uses its words to heal Cordelia, but not before Vocah has raised an new demon -- Darla. Wesley discovers the prophesy about Angel actually says he will become human at some point.