Morrey, Serge and Tony are sent to Mars to investigate the murder of William Baines, an electronics specialist who has been found dead in a crater. There are more than a hundred people working in Mars city, and at first the astrotecs, as Commander Morrison calls them, see no reason to suspect one more than another. However, investigations on the spot soon narrow down the field to a few suspects, and gradually all the clues begin to point in one direction. Morrey and Serge are sure that the case is solved, but Tony still has doubts, and he decides on an independent - and dangerous - piece of detective work.