Herbert Marshall, a well known stage actor, is a juror on a murder case. The accused is an actress, Norah Baring, who was found dazed near the recently deceased.

While the jury feels this is an open and shut case, a doubting Marshall hopes to prove the innocence of the young girl.

When he reverts to his acting faculties to apprehend the alleged perpetrator, the true murderer's cunning proves to be just as crafty.

A German version of the same film, called "Mary" (AKA "Sir John greift ein!"), was filmed at the same time, using the same set, but employed German speaking actors.

The scene where Sir John thinks out loud in front of a mirror was filmed with a recording of the lines and an orchestra hidden behind the set as post-dubbing was not yet possible.

Hitch makes his cameo about an hour into the film walking past the house where the murder was committed.