Serum obtained from a brain after a mass murder transforms the good Dr. Jekyll of London into the evil Mr. Blood.

The Expert is a British television series produced by the BBC between 1968 and 1976. The series starred Marius Goring as Dr. John Hardy, a pathologist working for the Home Office and was essentially a police procedural drama, with Hardy bringing his forensic knowledge to solve various cases. The Expert was created and produced by Gerard Glaister. The series was also one of the first BBC dramas to be made in colour, and throughout its four series had numerous high quality guest appearances by actors such as John Carson, Peter Copley, Rachel Kempson, Peter Vaughan, Clive Swift, Geoffrey Palmer, Peter Barkworth, Jean Marsh, Ray Brooks, George Sewell, Anthony Valentine, Bernard Lee, Lee Montague, Geoffrey Bayldon, Mike Pratt, Edward Fox, André Morell, Brian Blessed, Nigel Stock, Philip Madoc and Warren Clarke.