He was portrayed by Scottish-Peruvian actor Henry Ian Cusick.
Weber's British accent indicates that he either grew up in Britain, or America and was raised by British parents. Weber was an excellent painter and martial artist, but there was a darker side to him: he was sexually attracted to little girls. In 1982, when Weber was 16, he raped his 9-year-old sister Grace. He promised he wouldn't do it again, but he kept on raping her presumably until she wasn't little anymore.
In later years, Weber came up with a sob story that Grace hanged herself in 1982 after being raped by an unknown assailant. He eventually moved to New York and became a member of COAP, an organization dedicated to monitoring registered sex offenders. Along with serving as a community liaison with the media, Erik teaches children - particularly little girls - karate to use in self-defense against anyone who tries to abuse them. This, along with moving to a neighborhood full of registered sex offenders, became a perfect cover for raping little girls; he made sure the police were watching the other pedophiles so he could hide in plain sight. Weber also had excellent computer hacking skills, which came in handy when he wanted to deflect police attention by putting his own child pornography onto someone else's computer.
Detectives Elliot Stabler and Olivia Benson are investigating the disappearance of MacKenzie Burton. After finding emails between MacKenzie and another man, they track her to Grand Central Station, where they find her sitting next to and talking to Erik Weber. They arrest him, but he says that he is a member of COAP, and that he hates pedophiles because one had raped his sister years before.
Benson and Stabler learn that the boy MacKenzie was talking to is her former foster brother, and that they were planning to run away together. Weber was supposedly just trying to convince MacKenzie to go home. Weber is released from custody. He asks Detective Benson out, but she politely declines.
A 10-year-old girl is found in a supermarket, showing signs of having been sexually assaulted. The girl seemed even more traumatized when her nurse brings in a camera, saying that the rapist took pictures of her. The girl is identified as Rose Samonsky, and she says that her rape occurred at a children's playground called Laffy Play Time.
The detectives interview a falsely accused suspect who had been harassed by COAP volunteers, and once again question Erik. He promises to help and stay out of SVU's way, but complicates the investigation by leaking the victim's picture to the media.
When another little girl, Mandy LeCompte, is attacked and raped, Benson goes over to Erik's apartment to ask him of he knows anything. He shows her how he hacked into several Internet servers with child pornography, which include pictures of Rose and Mandy being assaulted. The images were uploaded to a computer belonging to Edwin Adelson, a middle-aged sex offender; Benson and Stabler arrest him, and Erik identifies him as a child molester on COAP's website. After his arraignment, Adelson commits suicide by driving his car into a truck, which causes an explosion. Benson introduces Mandy and her mother to Erik, who offers both of them karate lessons. Mandy recognizes Erik's voice; frightened, she urinates in her chair. Benson realizes that Erik is the real rapist.
Benson goes back to Erik's apartment and hits on him in order to draw out his true nature; sure enough, he rebuffs her advances. Benson then insinuates that she is "too old" for him, and that he puts on an act about hating pedophiles so people won't realize that he is one himself. Benson then reveals that Grace is alive, and Stabler appears with an adult Grace in tow. She tells the detectives what Erik did to her, and demands to know how many other little girls he has assaulted. Erik pleads for mercy, saying that he can't help himself, but Benson dismisses it as yet another sob story. Enraged, Erik attacks her, but she knocks him out cold. Grace grabs a knife, seemingly intending to kill Erik, but instead destroys a portrait Erik had painted of her as a little girl.
It is presumed that Erik went to prison and was expelled from COAP.