This was the 3rd of 3 Inspector Ernest Lamb series.
Double agent Cornelius Roos is about to be executed by the Gestapo until he provides extortion proof of evidence against a high ranking German official. Roos demands release or the info gets sent to Hermann Goering. Meanwhile back in England, Antony Rossiter, brother to Roos, is sent parachuting into Germany to contact Roos. Those are the opening gambits to a case for Inspector Ernest Lamb working on a case of murder. As always, Colonel Frank Garrett has his fingers in several pies.