A crucial difference between "Dual" and "Swan Song" is that here, Sarah is encouraged to discuss the prospect of replacement with her loved ones beforehand, whereas in "Swan Song," it's forbidden to reveal that you're considering being replaced.

In order for the replacement process to work smoothly, the double needs to spend as much time as possible with the original in order to learn how to essentially become them.

The trouble begins on the first day: Sarah realizes her double doesn't have cellulite or love handles, is a size smaller than her, and the double almost immediately begins asking about Sarah's boyfriend's favorite sexual positions, presenting as just a bit too eager to take over Sarah's life.

"When you're gone, I promise to love [your mom] as much as you do — maybe more," the double tells Sarah.

("Peter and I will probably make love when we get home tonight," Sarah's double tells the original as Peter and the double prepare to go on a date. "As you know, I tend to be loud, so I wanted you to be aware.") When Sarah tries to have her double decommissioned, the double exercises a right that Sarah must not have noticed in the fine print when she initially agreed to this process: If a double feels like they've established their own identity, they can challenge the original to a duel to the death, which are filmed and broadcast as a popular TV show.

Kicked out of her own apartment and with a year until the duel takes place, Sarah hires a personal combat trailer named Trent (Aaron Paul) and begins learning the most effective ways to kill her double.

But as evidenced by this film's title ("Dual," not "Duel"), Stearns is not as concerned with creating a gruesome "Battle Royale" as he is with exploring the dynamics between characters and the contradictions and conflicts that arise when two of the "same" person come together.