<P> The horns are revealed to force people around Ig to tell him their darkest secrets and desires, which, under Ig's bidding, they act upon . Ig goes to visit his parents, but under the power of the horns his mother reveals that she doesn't want him as her son, while his father tells him that he is worthless without Merrin and that a friend of his helped him burn down the lab where DNA tests were being conducted . Ig goes to a bar, where he goads the reporters into a brawl and attempts to find evidence that he didn't kill Merrin . Several people confess their deepest secrets, and the bartender burns down the building . </P> <P> From one of the confessions Ig also learns that the new witness for the case is from the diner where Merrin broke up with him the night she died . Ig finds the waitress, and discovers that she has been fabricating her stories to become famous . When Ig talks to Terry, he learns that Terry had driven Merrin from the diner the night she died . When he touches Terry, Ig sees what happened that night: Merrin left the car en route to her home and ran into the woods; Terry passed out in the car, and woke up the next morning with a bloody rock in his hand, finding Merrin dead under the treehouse . Afraid that he would be implicated, he fled . Infuriated, Ig assaults Terry until he is arrested by Eric Hannity, a police officer and another childhood friend . The next morning Ig is released from jail with Lee's help, discovering that Lee had been wearing Merrin's cross necklace and as a result couldn't see Ig's horns . </P> <P> Ig realizes that snakes are following him wherever he goes, and uses them to exact vengeance against the waitress . He also gets Eric to act on his feelings for his fellow police partner (who reciprocates his feelings) and forces Terry to overdose on drugs, causing Terry to be tormented with memories of Merrin's death . Ig meets Lee by the docks and pulls off Merrin's necklace; exposed to the horns, Lee falls under their influence, admitting he killed Merrin . In flashbacks, it is shown that Lee was also in love with Merrin and was deeply jealous of Ig throughout their childhood . Lee followed Merrin into the woods, thinking that she had broken up with Ig to be with him, and in a jealous rage raped her, killed her with a rock, planted it on Terry, and stole her necklace . In the ensuing confrontation, Lee overpowers him and lights him on fire in his car, causing Ig to drive into the bay, claiming that Ig confessed to the crime and committed suicide . In reality, with the power of the horns, Ig survives, horrifically burned and disfigured . </P> <P> Merrin's father, who now believes Ig's innocence, gives Ig the key to Merrin's lock box . When Ig puts on Merrin's cross, his body is restored and his horns disappear . In the box, he finds a note from Merrin that explains that she knew he was going to propose, but she was dying from cancer and didn't want him to suffer, so she pushed him away under the pretense of loving someone else . </P>

Who killed the girl in the movie horns