The action of the novella takes place in the twenty-third century, when humanity has actively begun expanding the boundaries of its knowledge of the universe. With the help of timephage equipment (a timephage is a “time eater”), any material body can be instantly transferred to any point in space. And then something goes wrong in the system: dispatched cargoes begin to disappear and fail to reach their destinations, which is considered impossible in principle. A series of mysterious inexplicable events occurs; in places of increased danger in space and on Earth, a “sign of trouble” appears—a footprint of a foot that stepped on a butterfly.