Abby is a main protagonist from the movie Let Me In.
Abby who looks like a 12 year old girl has been nomadic for decades with her caretaker Thomas, whom she poses to be her father. She's a vampire, and he regularly kills humans so she can drink their blood. One day they come to Los Alamos, where Abby moves into a run-down apartment complex.
Abby meets Owen in the playground in front of her new apartment. First she wants him to get out of there and be left alone. She also tells him that they cannot be friends. But over time, the two become friends.
Thomas has in the meantime killed someone and brought their blood to Abby, but lost much of it in an accident. Abby is furious because she is starving because of his incompetence, while Thomas says resignedly that he doesn't know if he's tired of the murder and wants to be caught by the police. Eventually Abby regrets her outburst and treats Thomas a little better.
The following night she meets with Owen again, and they both like each other a little more now. But as soon as Owen has left, Abby is hungry and goes off to kill a man who happens to be passing by and to feed on his blood. When she tells Thomas what she did, he yells angrily at her and leaves the house to hide the body. But this body is found only a few days later.
In the meantime, Owen has given Abby a Morse code so that they can tap through the walls to communicate.
Finally, Abby goes on her first date with Owen. Both have fallen in love, but Abby is reluctant to reveal her true nature to Owen. For his sake, she wears shoes instead of being barefoot, although she doesn't mind the cold. To his delight, she also eats sweets, but has to spit them out shortly afterwards because as a vampire she can only feed on blood. After Owen tells her how much he is bullied and beaten at school, Abby perks him up to fight for himself and to fight back. She also promises to help him if his strength is insufficient.
At one of the next meetings, Owen tells her that this time he fought against the bullys and even injured one of them. Abby then gives him his first kiss.
The night after that, her caretaker Thomas goes out again to get blood for her, but it fails catastrophically and he is caught. In order not to betray her, he disfigured his face with acid before the police can arrest him and he was taken to a hospital. Abby hears what happened over the radio and goes to the hospital, where she poses as Thomas' daughter. When she finds out which room he is in, she flies up. Thomas regrets failing Abby's foraging, and Abby regrets she mistreated him so many times. Thomas offers his blood to Abby and after she suckles his blood out he falls out the window and die.
That same night Abby flies to Owen and asks him to invite her. When she comes to his room, she strips naked and lies down in his bed to cuddle with him. Owen asks Abby if she would like to be his girlfriend, but she refuses at first. However, after Owen has assured her that nothing needs to change between them, she accepts. Before she has to leave his apartment shortly after daybreak, she leaves him a romantic poem.
The following night, Owen invites Abby to visit a secret basement room. He wants to offer her a blood pact there, but when Abby sees his blood, she loses control and reveals herself to him as a vampire. She can control herself just enough to spare him and instead attack a woman who is walking her dog outside.
The next day, Owen comes to Abby's apartment. He confronts her, but wants to leave the apartment quickly. When he asks if she'll let him go, or if she'll hurt him too, Abby looks terribly sad and says that she said beforehand that they can't be friends, but lets Owen leave the apartment.
Not long afterwards, she enters his apartment. However, Owen refuses to invite her in, and Abby begins to bleed all over. Startled, Owen now invite her in and gives her a desperate hug. Abby realizes that although Owen was scared of her at first, he really loves her, and she also loves him. She takes a shower there, but has to leave the apartment when Owen's mother walks in.
Owen comes to her apartment shortly afterwards and stays with her for the night. The next morning, however, a police officer broke into the apartment, who realized that Abby was behind the series of murders. He surprises Owen and Abby, but Abby, to Owen's horror, kills him. After Owen has helped her hide the body of the policeman, she kisses him and says that she has to leave now.
One evening after they said goodbye, however, Abby goes to the swimming pool where Owen is. There she sees that the Bullys are trying to drown or mutilate him. Screaming with anger and indignation, she smashes a window and breaks into the swimming pool, where she brutally kills all four bullys. In doing so, she keeps her promise to Owen to protect him.
Shortly afterwards, Owen and Abby leave Los Alamos together. Abby sits in a large suitcase to be protected from the daylight, while Owen sits with the suitcase on a train that leaves in broad daylight. After the conductor has checked Owen and has left, Abby knocks on the inside of the suitcase with Morse code that she loves Owen, which Owen replies the same.
- Abby and Owen are originally based on a novel, the protagonists of which, however, are called Eli and Oskar. Since the film is far enough away from the book, Abby and Owen are different characters, and not identical to those in the book.
- The film has an ambiguous ending about the ultimate fate of Owen. There is both the possibility that he will become Abby's new caretaker or that she will turn him into a vampire. However, the actress who plays Abby said in an interview that Abby really loves Owen, unlike her caretaker Thomas.
- During the film, Abby said several times that she was not a girl. In fact, Eli from the book is a castrated boy who is mistaken for a girl or pretends to be a girl. However, Abby is actually a girl, which is why this phrase doesn't make sense in this context. Unless this statement is interpreted to mean that she is carefully telling Owen that she is not a human.