A magazine reporter, Jeff (Jake M. Johnson), and two interns, Darius and Arnau (Aubrey Plaza and Karan Soni), track down the author of a classified ad, Kenneth (Mark Duplass), who has advertised for a partner to time travel with him, "bring your own weapons, safety not guaranteed, have only done this once before."
The reporter is a bit of a jerk, letting the interns do all the work while he uses the road trip to track down an old girlfriend, and to get shy Arnau to enjoy life a little. Darius is able to meet Kenneth and gain his trust. He teaches her self-defense and she drives the getaway car when he steals some technical equipment he needs. They slowly fall for each other even though Kenneth reveals the reason he wants to go back is to save his girlfriend Belinda from an accident that kills her. Jeff is convinced Kenneth is crazy but Darius is no longer sure. Kenneth is paranoid and keeps looking for "government agents" who he says are following him, and the others eventually see a couple of suits in a government vehicle doing just that.
The magazine editor researches Belinda and discovers that she is alive, only an hour away; Darius goes to interview her and then confronts Kenneth. He insists that if she's not dead, they must have been successful on their mission.
When Kenneth finds out Darius works for the magazine, he runs away, feeling betrayed. Darius runs after him and tells him truthfully that everything else between them was real. He tells her that mission has changed and that he is going back now for HER. He brings her into the time machine, which looks like a small boat at a lake dock. Jeff, Arnau and the government agents arrive just as the machine is firing up. As the four of them watch, Kenneth and Darius kiss, the machine revs up and the whole boat disappears in a flash of light. The movie ends with a clip of the taped message Darius made of Kenneth discussing his search for a time travel partner.