The departure of Professor Sam Ryan in the last series means that the forensic pathology department is now headed by doctors Leo Dalton and Harry Cunningham. Firmly established new recruit Nikki Alexander has become an indispensable member of the department. Together they must tackle a variety of mysterious and suspicious deaths: a spate of drive-by shootings, the result of a ongoing local turf war; a possible copycat sex killer preying on women in both London and Amsterdam; and an emotional return to Sheffield for Leo, to track down the crime boss who murdered his wife and child.