When physics student Stillman (Butterfield) is broken up with by his girlfriend Debbie (Sophie Turner), he is crushed. Through his heartbreak, Stillman is inspired to win Debbie back, and uses his brains to create a time machine with his best friend Evan. Using the time machine, Stillman seeks to change the course of his relationship with Debbie and prevent her from breaking up with him. Can Stillman allow nature to dictate the course of their relationship, or will he continue to manipulate time to save it?