The crew of Voyager discovers a strange ocean world in space and offers to help the inhabitants find out why the ocean is losing water to space. They find the forcefield maintaining the planet's integrity is breaking down. Tom Paris directly disobeys orders in an attempt to save the planet, which results in his demotion to Ensign and being placed in the brig for thirty days. Paris tells the story of this episode in a letter for his father to pass the time in the ship's brig. When first encountering the world, Paris interrupts Kim in the middle of his Chaotica holodeck adventure.

The Doctor discovers evidence that his short-term memory files may have been tampered with and altered with some events deleted. He launches an investigation into whom or what could be responsible and is shocked at who it is and why they're doing it. The Doctor recalls the death of crew member Jetal and believes he was responsible.