While on a mapping mission, the Enterprise receives an outdated transmission from the volcanic star Cepheus. A flash of light from the planet passes through the ship and disables all dilithium crystals. Soon thereafter, the crew begins to shrink. With no cure in sight, it becomes increasingly difficult for the Starfleet officers to handle the ship's controls.
- While investigating the site of a supernova, the Enterprise crew discover that they are shrinking in size. If a way cannot be found to stop their condition, they will soon be too small to control the ship. The answer may lie in a lost Earth colony, whose members have been affected by the same unusual radiation.