[4] The screenplay was by Tully and Maurice J. Wilson based on the short story "They Also Serve" by Gerald Anstruther and Paul White.

In a plot twist, it is revealed that Turganev was working for British Intelligence, who suspected Skelton and wanted to catch his spy ring.

The Monthly Film Bulletin wrote: "Placid and plodding, this spy story is distinguished only by a few nice touches of characterisation.

Indeed, the most exciting moments are the games of chess during which defector Stephen Murray passes vital secrets to communist squire, Alan Wheatley.

There's a valiant attempt to put a sting in the tail, but only lab assistant June Thorburn fails to see through the slenderest web of deception.