The film revolves around a young American man named Simon who is visiting Paris and his relationship with a Middle Eastern prostitute and a French woman he meets on the metro.

After his girlfriend of five years, Michelle, leaves him when he aggressively accuses her of cheating on him, college graduate Simon takes a trip to Paris.

On the day when he is supposed to leave the apartment he is staying at, scours a nearby train station for a person or people to beat and rob him.

While in bed together, she tells him in English about her abusive ex-husband, then in French about how she miscarried and her husband raped her before taking her to the hospital.

After an unsuccessful attempt to blackmail a cop, they find success in René, a man who pays them in exchange for their silence.

The website's critics consensus reads: "Though its bleak themes may be off-putting for some, Simon Killer is an engrossing, effective character study of a brutal, enigmatic figure."

On Metacritic, the film has a weighted average score of 63 out of 100, based on 18 critics, indicating "generally favorable reviews".