Tim (Domhnall Gleeson) is 21 years old. His father (Bill Nighy) told him that the men in their family have the ability to travel through time and can go back to the past. So Tim tried it with doubt and returned to the summer, where he tried to change his relationship with his crush, but found that no matter how he traveled through time and space, he could not make someone who didn't love you fall in love with you. Then Tim came to London and became a lawyer. He fell in love with a beautiful girl Mary (Rachel McAdams), and he tried to become Mary's boyfriend through several time and space travels. Later, he tried to save a failed drama through time travel, to improve his sister's life, to get along better with relatives and friends, and spend every day of his life.