A man named Simon is convicted and imprisoned for his involvement in destroying a space station known as Filament Station. He is sent to a newly discovered moon and forced to pilot the SM-13 (a submarine with a sealed porthole nicknamed the "Iron Lung") through the depths of the moon's ocean of blood. In order for Simon to see, he must take still images using a crude camera, and he receives limited communication from his crew on the surface via a radio. In exchange for completing the mission, Simon is promised freedom. During the dive, Simon captures images of a large skeleton on the ocean floor and is briefly brought to the surface before being tasked with collecting a sample of the skeleton. Simon demands to be freed and activates the camera, but the crew's commander berates him, explaining that the camera is an x-ray imaging device, which has heavily irradiated the crew outside of the submarine.