Simon realizes he didn't kill her because the bite was on her foot—a part of the body he finds repulsive. He tracks down Quinn, who is the real killer, and kills him in a fight.
Following his painful breakup with Clary at the Seelie Court, Simon seeks a distraction with a vampire named Quinn. He wakes up with a "vampire hangover" and no memory of the previous night, only to find a dead mundane (Heidi) nearby. Shadowhunters: 2Г—15
Simon initially fears he killed her, especially after Luke’s partner, Ollie, finds his fingerprints at the scene. Simon realizes he didn't kill her because the
Despite the ordeal, Simon tells Clary he needs time away from her to process his emotions. Shadowhunters 2×15 Review: “A Problem of Memory” who is the real killer