Before an estranged couple is killed in an unthinkable tragedy, they designate two guardians for their children—a man and a woman who are essentially strangers and who have nothing in common except their compassion for the couple's three orphaned children. Thrown into this strange semblance of family, Sean McGuire and Lily Robinson work together to establish some kind of normalcy for the grief-stricken children—and in the process discover the possibilities that make everything seem worthwhile.