Gillian, a struggling filmmaker, is told by two close friends that with her cunning, intelligence and ability to rationalize whatever she wants to believe in she would make a good murderer. This innocent jokey remark gives her the idea for a short documentary to research the truth behind the compliment. She interviews her friends in classic murder locales -- empty parking lots, in the middle of the woods, the docks. For the finale, Gillian decides to plot the perfect murder and chooses as her hypothetical subject her friend Chase's abusive girlfriend. When she tells Chase about the project and asks him to let her shoot the ending in his house, with her describing how she'd do it, he's horrified. Gillian is surprised he doesn't get the joke and doesn't know why he's defending his cruel, destructive domestic partner. It ends their friendship and Gillian shoots an alternate ending for the film.

Three years later: Gillian's filmmaking career is struggling so she decides to resurrect her abandoned short (which she never released) and try to mend her relationship with Chase at the same time. But while she shoots more material the research, combined with stress in her career, seems to be getting under her skin. Even her boyfriend, Keith, doesn't seem to believe in her. Frustrated at the lack of support for her art, Gillian decides to overcome the doubts around her another way: she will prove that she can commit the perfect murder.

But doing that inherently denies her the recognition that she craves. Nobody believes she killed someone, nobody believes she can make a movie, people just don't believe in her... and it unhinges her even more. After accidentally-ish killing Chase during their reconciliation, Gillian goes on a murder spree culminating with a final bloody act that nobody would dare deny her credit for.