[1] The cast includes Michael Redgrave, Patricia Roc, Sally Gray, Paul Lukas and Hartley Power.

The plot focuses on a man who becomes drawn to the wife of a jealous magician - after spotting what appears to be a murder in their flat.

Pat is a hotel switchboard operator at an exclusive London apartment block (the exterior location is actually Dolphin Square[citation needed]).

One morning, Peter is on the Tube on his way to work when he spots what seems to be a murder being committed on a balcony: a man stabbing a woman.

Deciding to investigate, Peter and a policeman arrive at the residence, but the man there, Zoltini, tells them that they were merely rehearsing an illusion for a stage act.

Peter offers Zoltini money to ease his alleged problems, and takes the dummy knife as a souvenir of the event.

Later, as they are due to appear on stage, Zoltini and Vivienne have an argument, leading to him slapping her in the face immediately before the show starts.

They are alarmed by a knock on the door, but it is the night watchman saying the river police pulled Zoltini out alive.

But as a happy Pat and Peter go past their window on the Tube train, Zoltini finds Vivienne's contract and a ticket to New York which Max put in her purse and shoots her dead.

[4] Filming also took place at the Thames, Embankment, the Chelsea Palace, the Savoy Court, Dolphin Square and on the London District Railway.

[5][6] On 8 June 1939, Kinematograph Weekly announced that exterior scenes would "be filmed at Baron's Court Underground Station and in Parliament Square.

[7] In the past when Patricia Roc saw several West End productions, she saw "many of the great actors" (including Michael Redgrave) perform on stage.

Additionally the Monthly Film Bulletin said that, "Patricia Roc gives a charming little character study of a working girl wife.

"[16] Although the New York Times said that it was "muddily photographed and poorly directed", Michael Hodgson considers the film to be one of Mason's "interesting films" as well as "a dark and disturbing remake of Maurice Cam's French circular drama Metropolitain" in his biography about Patricia Roc.

[17] Robyn Karney in Radio Times described the film as "a short, modest but intriguing British-made thriller with a satisfyingly neat twist in the tale".