A man is found by Chief Superintendent Buchanan sitting on the steps of Whitehall. The man has apparently lost his memory. He utters only three words: I witnessed murder...

Buchanan calls him Michael, hand him over to a reluctant Tweed, ex-Scotland Yard detective, now Deputy Director of the SIS. Events lead Tweed with his assistant, Paula Grey, to desolate Dartmoor, accompanied by Michael. There they discover two skeletons. Later, two more -- one in London, the fourth on a Sussex canal boat.

The wealthy Volkanian family, from Armenia, have a mansion on Dartmoor. Are they involved? Key characters are Lucinda Voyles and Anne Barton.

There is a new development. A strange freighter, cargo holds empty, is spotted heading from the Mediterranean towards the Cornish coast. Tweed suspects the vessel is linked to the four horrific murders.

The relentless pace of Tweed's investigation accelerates. Can he break the case before a sinister deadline? He fights ruthlessly to do so -- in a riveting double climax.