DS Sean Stone is an intense, socially awkward misfit who is obsessed with uncovering behavioural patterns to help locate missing people. Sean's bosses feel that he is a liability on his own and needs someone to work with him to keep him under control. That person is Ruth Hattersley, a maternal figure who is an analyst with the Missing Persons Bureau. At first Sean is reticent to work with her, but he eventually realizes that the two of them make a good team. Ruth's ability to connect with people and Sean's expertise in locating missing persons strike a perfect balance in an otherwise rocky partnership.