In the Headquarters of the T.I.A. (Terminal Intelligence Agency), someone has stolen Professor Bacterio's most dangerous invention, the D.O.T. (Demoralizer of Troops), an artifact that ends up in the hands of a very short, wacky dictator who is ready to use it for criminal purposes. The T.I.A Chief, though, is firm in his resolve: if he wants to get the D.O.T. back, he must NOT count on his agents Mortadelo & Filemon. But when the crime fighting duo discover that the T.I.A. has engaged a cocky and slimy detective from outside the agency, they decide to act at their own risk, even if that risk involves all of Humanity.

A criminal produces an uncontrollable laughter to the population and Mortadelo and Filemón will have to stop him.