When Deimos, the owner of a pawnshop, receives a visit from his superior, Phobos, they present their Martian identifications to each other. Deimos is a Martian agent, based a long time ago at an Earth outpost disguised as a pawnshop to observe Earthlings. Phobos, worried over Earth's advent into atomic energy, has come armed with a time-controlling device to try to understand the concept of "murder." Soon they receive a message to visit a low budget hotel and witness a murder in its lobby. On arriving, they identify blonde Carla Duveen waiting for her boyfriend, Bert Hamill, to return from sex with his lover. Phobos uses the time-controlling devise to repeat the murder many times to understand its details; however, the experiment runs out of control, and they receive a report that the future will be affected by their fiddling. Can they fix the problem?
—Claudio Carvalho, Rio de Janeiro, Brazil