The Eagle uses sky writing to make threats against a corporation. Nathan Gregory owns a travelling fairground and is thought to be the Eagle. Craig McCoy is a pilot who goes looking for the Eagle when Gregory turns up missing.

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.