Bob Norton, seeking his brother's killer, tangles with outlaws, wild horses, and a "wild" boy.

A mysterious criminal known as The Whispering Shadow commits crimes by means of a gang he controls by television and radio rays. Jack Norton, whose brother was murdered by The Whispering Shadow, suspects that the eerie Professor Strang - whose ghostly wax museum contains figures far too lifelike - may be involved in the crimes.

A scientist is turned into an ape man.