A lavender rat, which has escaped from a laboratory, accidentally stows away on a space station. In addition to the scientists, technicians, and astronauts on board, a lonely young boy attracts the rat's attention, and she watches him in an effort to get food. When the two encounter each other, the boy is amazed to discover that the rat has been trained to communicate in sign language and by typing. The two misfits begin a friendship based on need, as they fight off efforts to discover and stamp out the stowaway.