Newly promoted Sergeant Arthur Diamond is glad of a little action, when not one, but two missing person reports are made in one day. Meanwhile the station's new lieutenant, Billy Doran, has challenges of a different kind. As the Doran sisters prepare for Maeve's Christmas wedding, Bridie surprises everyone, and at the Cook County morgue the new Coroner makes a shocking discovery. Before long all of these threads will lead Diamond back home to Canada and the rest of the Doran clan to places none of them expect.