First broadcast 21st March 1974.

Craven is put in charge of security for a vital debriefing exercise being held at a derelict mental institution.

George Sewell ... Detective Chief Inspector Alan Craven
Paul Eddington ... Strand
Anthony Nicholls ... Colonel Lang
Cyd Hayman ... Nadya Chelnov
Geoffrey Chater ... Sir Gerald Pastor
Paul Antrim ... Detective Sgt. Maguire
Richard Cornish ... The Young Lang
Barbara Kellerman ... Michelle
Richard Steele ... Davies
Timothy Morand ... Claude (as Tim Morand)
David Webb ... S.S. Officer
William Redmond ... French Colonel