The Scarlet Clue

The Scarlet Clue is a 1945 American mystery film directed by Phil Rosen and starring Sidney Toler, Mantan Moreland and Ben Carter.

The film is also known as Charlie Chan in the Scarlet Clue (American informal title) and Charlie Chan: The Scarlet Clue in Australia. The film is in the public domain due to the omission of a valid copyright notice on original prints.

Plot
Charlie Chan is working for the United States Government tracking down the theft of radar secrets. When the man they are tailing is murdered, the only clue is a footprint in blood. Chan. His "Number Three Son" Tommy and their chauffeur Birmingham Brown's investigation leads to a radio station. Birmingham runs into his old friend Ben Carter at the station with other suspects including the radio station staff, stars and cleaning woman. The closer Chan gets to solving the mystery, the more mysterious murders happen.

The science lab where the radar secrets are developed shares the same skyscraper floor with a radio soap opera studio, the program apparently under the thumb of its tyrannical sponsor, Mrs. Marsh. The lab also has a weather chamber that can create below zero blizzards or extreme heat. Tommy Chan and Birmingham spend a great deal of time comically trapped in it.

It is quickly established that the station manager, Ralph Brett, is part of the spy ring. But he only communicates with the Master Spy by a clever series of telephone relays. The leader has invented a clever poison that causes death in conjunction with lighting a cigarette. Blackmailing actress Gloria Bayne and genial ham actor Willie Rand meet death by this device.

When the Leader judges Brett to be a liability, he is lured to a freight elevator with a trap-door floor that drops him seven stories to his death.

Unnerved by the murders, another member of the ring offers to lure the Leader into the open with a false distress message.

During an in-and-out corridor chase on the 7th floor, the Leader is revealed to be Mrs. Marsh...who dies when she panics and accidentally steps into her own elevator trap.

Cast

 * Sidney Toler as Charlie Chan
 * Benson Fong as Tommy Chan
 * Mantan Moreland as Birmingham Brown, Chauffeur
 * Virginia Brissac as Mrs. Marsh
 * Ben Carter as Ben Carter
 * Robert Homans as Capt. Flynn
 * Jack Norton as Willie Rand
 * Janet Shaw as Gloria Bayne
 * Helen Deverell as Diane Hall
 * Victoria Faust as Hulda Swenson / Janet Carter
 * Leonard Mudie as Horace Karlos
 * I. Stanford Jolley as Ralph Brett
 * Emmett Vogan as Hamilton of the Hamilton Laboratory