When a man is found murdered inside his supposedly impenetrable doomsday fallout shelter, the squad must figure out how and why he was targeted. Jane finds it difficult to focus on the case when she discovers Korsak is looking into retirement and Frankie is keeping a secret of his own.

With Maura at a Medical Examiner's convention, Jane needs Susie's help and crime scene dioramas to solve the perfect murder. Meanwhile, Korsak is visited by the son of an old friend and forced to deal with painful unfinished business.