Illegal body building drugs combined with mind bending additives cause a series of deaths around the muscle scene in Glasgow. In a race against time to find the source of the deadly drug the Maryhill team call on the help of a famous chemistry professor at the University. But is he helping or is he the source of the drug?

A school master is beaten to death with a cricket bat by an unknown assailant. 60 years later, the body is found by students on a cross country run. Douglas Flemming identifies the bones as Friedrich Zwanziger, a strict disciplinarian who disappeared while collecting beetles. As the investigation proceeds, McVitie discloses that he is on the board of governors.