Harry Riebauer

A strangler is loose on a British estate, and he not only strangles his victims but brands an "M" onto their foreheads before he decapitates them.

An Australian woman arrives in London to search for her sister, and finds her involved with a heroin-smuggling gang that is under attack from an unknown rival who is methodically assassinating them with a shot to the head.

A group of vigilantes hang wrong-doers.

A thoroughbred is highly favored to win an important upcoming race, and several people connected to the horse begin to fall victim to a mysterious assailant. Meanwhile, an equine veterinarian is blackmailed to compromise the horse.