Peter Garber was murdered in the very beginning of the film, and it was Richard Castle's investigation that led him and daughter Alexis to the "prison," where they met Emily. Emily expressed shock over Peter's escape, and it increased when she was informed that Peter was killed. Dr. Barbara Lillstrom, who conducted the experiment, was not only suspected by Castle, she was arrested by him under the belief that she was having an affair with Peter and killed him to keep him quiet. Lillstrom denied the claim but revealed that Peter's affair was with none other than the college's dean, Carla Feller, who became another suspect.
After Castle and Kate Beckett returned to the prison to figure out how Peter escaped, they not only found out how, they also learned that he had an accomplice in the escape, who was revealed to be none other than Emily. The fact that Emily was the only one who returned to the prison also revealed her as Peter's killer, and regarding a motive, it was uncovered that Peter's affair with Carla led to her handing Peter a scholarship that Emily was vying for, leaving her angry and vengeful towards Peter. As Emily revealed to Castle and Alexis, Peter was a guard in the experiment, but was demoted to becoming one of the prisoners due to his genial nature to the "inmates." On that evening, Emily helped Peter escape through the vent above them, with both of them running through Central Park following their escape. Emily turned heel afterwards by shoving Peter into a protruding tree branch, killing him in an act of revenge before returning to the prison.
Emily was interrogated by detectives Kevin Ryan and Javier Esposito regarding her role in Peter's escape, which she denied. When the scholarship was mentioned, Emily stated that Peter won fair and square, only for Ryan to reveal Emily's knowledge that his affair with Carla led to the scholarship, as well as her murderous plan upon finding out. After her continued denial, the evil Emily confessed, but claimed that the experiments made her kill Peter, despite voicing her bitterness over not getting the scholarship. The villainess was arrested (off-screen) following her confession.
- Madeleine Coghlan later played psychotic villainess Maxine in Holidays.
- "It wasn’t me. (Esposito: "Stop lying, Emily!") It wasn’t! It was a different me. That experiment messed with my head! After we escaped I just...snapped! It was so unfair! I had worked so hard, did everything right! When Peter ran into the park I went after him. Then I saw that tree branch. Why did I do that?" (Emily's confession to killing Peter Garber)