A coin dropped to the ground, green channel and yellow channel on the Brooklyn Bridge on July 4. Young couple Kate (Lynn Collins Lynn Collins) and Bobby (Joseph Gordon-Levitt Joseph Gordon-Levitt) are deeply in love, but when they come to the Brooklyn Bridge, they entrust each other's fate on a small coin. So the seemingly ordinary day of July 4 became very meaningful to the two of them. When the coin was flipped to the ground, Kate and Bobby ran quickly in two opposite directions, and their future was unknown. Reality is immediately divided into two parallel spacetimes. In the green channel, Kate and Bobby come to Kate's home in Brooklyn and spend a quiet and happy day, while in the yellow channel, they inexplicably come to crisis-ridden Manhattan and are involved in a life-and-death robbery. On the verge of extinction.