While teaching the cat people of a planet war strategies, Oon wanders from lecture to lecture feeling unneeded and worthless. Gillian discovers the planet houses a Nightwalker, which is kept behind enormous tall doors sealed with a gold symbol -- a design that even it cannot cross. Oon accidentally knocks it off releasing the Nightwalker whose only purpose is the destruction of every living thing. He first destroys the Monster Minds as he had to promise Oon, but then he's after Jayce. Flora and Gillian go in search of the symbol while Jayce and Herc try to keep the Nightwalker away from the city. The symbol is given back to Oon who propels himself to the back of the Nightwalker joining Jayce who has found the place where the symbol fits to shut him down. Oon's self esteem is restored when he is asked to teach a class.