 The Brittens are involved in a fatal car crash . As a result , Michael Britten , a Los Angeles Police Department ( LAPD ) detective , begins to live in two separate realities . In one reality , in which he wears a red wristband , his wife Hannah Britten ( Laura Allen ) survives the crash , and in the other reality , in which he wears a green wristband , his son Rex Britten ( Dylan Minnette ) survives . Michael does not know which reality is real , and uses the wristbands to differentiate the two . 
