Rhoda Williams (Brit Marling), a bright young woman accepted into MIT's astrophysics program, aspires to explore the cosmos. A brilliant composer, John Burroughs (William Mapother), has just reached the pinnacle of his profession and is about to have a second child with his loving wife (Meggan Lennon). On the eve of the discovery of a duplicate Earth, tragedy strikes and the lives of these strangers become irrevocably intertwined. Estranged from the world and the selves they once knew, the two outsiders begin an unlikely love affair and reawaken to life. But when Rhoda is presented with the chance of a lifetime to travel to the other Earth and embrace an alternative reality, she must make a difficult choice.