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.

The planet is facing a great threat. During the worst drought ever known, a group of wrongdoers are in the process of finishing all the reserves of water that remain on Earth. The best secret agents in the world meet urgently, but they don't even have a clue. To make things even worse, the evil Botijola plans to sabotage the meeting. His intention is to convert the water into a substitute. In order to do this, he also tries to kidnap mad Professor Bacterio and get him to work for him. However, there are two things Botijola wasn't expecting. On the one hand, Bacterio, before being kidnapped, hid the parts of his invention in different historical moments, using a time machine. On the other hand, there are two international agents who haven't turned up at the sabotaged meeting, two agents who become the world's only hope: Mortadelo and Filemón.

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