Police detective Michael Britten (Jason Isaacs) is newly returned to work after being in a car crash along with his wife Hannah (Laura Allen) and his son Rex (Dylan Minnette). After the crash Britten discovers that every time he goes to sleep he switches between two realities, one in which his wife died in the crash and one in which his son died. In the reality where his wife is alive he is partnered with rookie Efrem Vega (Wilmer Valderrama) and is seeing a confrontational department-recommended psychiatrist Dr. Lee (BD Wong). His wife has redecorated the house and begins pushing him to move in an apparent effort to move past their son's death. In the reality in which his son is alive, Britten maintains his long time partner Isaiah 'Bird' Freeman (Steve Harris) and sees a more nurturing psychologist, Dr. Evans (Cherry Jones). His son, previously a football player, has recently returned to playing tennis, and is coached by Hannah's former doubles partner Tara (Michaela McManus). Britten remains unsure which of the two realities, if either, is real, and begins to worry he is losing his sanity when details begin to cross over between the two.