[1][2] The screenplay concerns a cashiered Royal Naval officer and a young woman who join forces to solve a murder and hunt down a German spy ring.

[3] The film features a single song sung by Phyllis Stanley, "Toddle Along" (Ben Frankel, Moira Heath).

Commander R. F. Heritage is dismissed from the Royal Navy during the Second World War after being found guilty of losing some top secret documents.

Meanwhile a young Canadian woman, Miss Verity, arrives at the cottage and finds Mary dead, clutching a note with the words "Child's Theatrical Agency".

Back in the hotel, experts in disguise decode the musical notation played by the harmonica player proving the sinister plot.

The Monthly Film Bulletin wrote: "Joyce Howard is very attractive as Laura, James Mason is good as Heritage, and Tom Walls is suavely sinister as Child.

There is a long and distinguished cast, including Edward Rigby as an old petty officer who supports Heritage through thick and thin.

"[5] Radio Times noted "an old-fashioned, run-of-the-mill and unlikely espionage thriller-come-romance, it was topical during the Second World War years, but is rather unrewarding now.

"[6] Britmovie wrote, "there are capable performances from all involved but it’s Tom Walls, the urbane Aldwych farceur, who steals the limelight when cast against type as a charming villain.