Grimmon, a Jezark, has crash-landed on Earth. Though he survived, his craft is a wreck. As he surveys the area around him, he is approached by two natives. They react in fear at the sight of him and throw their spears at him. He is unharmed and shoots them with his blaster. He explores the nearby area and looks down on the city of Athens.
The Doctor decides that Leela needs to learn about comedy. He takes her to ancient Greece, birthplace of comedy. She is dressed for the part, but the Doctor is not. As they walk the streets of Athens, however, strange looks are directed at Leela. She notices that there aren't very many women about.
They head for the amphitheatre, where the Doctor promises they will see a comedy. They see a play written by Aristophanes, in which Socrates is mocked. Leela does not understand why the wise man is mocked. The Doctor tries to explain, but gives up and instead takes Leela to the home of Anaximander, who is hosting a gathering. The Doctor and Leela crash the party and are welcomed by Anaximander, who introduces his guests: Socrates, Aristophanes, Euripides and Plato. The Doctor introduces Leela as his wife from Sparta. As they discuss Aristophanes' play, a strange "bird" is heard. Suddenly, Socrates' face goes blank and he leaves. The Doctor's sub-plasmic beam detector (the "bird" sound) has alerted him to a signal that should not be on Earth at this time. He excuses himself, leaving Leela behind, but after listening to the men's conversation without understanding it, she follows the Doctor.
The Doctor and Leela follow the signal, with the Doctor confiscating Leela's knife. They track the signal to where Socrates is standing by a wall. The wall starts to glow and Socrates walks through it. The Doctor realises that someone has used a de-atomic transformer on the wall, and he and Leela hurry through it. They continue to follow Socrates, who eventually arrives at Grimmon's crashed spaceship. Socrates starts working on the ship, but doesn't respond to the Doctor.
Leela senses an attack and knocks the Doctor out of the way. Grimmon appears, and he and the Doctor discuss Grimmon's predicament. The Doctor is horrified that Grimmon is using Socrates' brain to repair his ship, and even more horrified that on takeoff Grimmon's ship will destroy the surrounding area. Grimmon doesn't think it's important, as this planet is not significant. The Doctor suddenly agrees with Grimmon, but then grabs him and holds Leela's knife at his chest. Leela takes Socrates and heads for the TARDIS, where they will wait for the Doctor.
The Doctor arrives at the TARDIS, and Socrates returns to his senses. The Doctor sends him on his way, and after he leaves, the Doctor and Leela see Grimmon's ship take off. Leela thought the Doctor had killed him, but instead he helped repair Grimmon's ship and sent him on his way. The Doctor and Leela leave Athens as well, with the Doctor lamenting that "every other person on the street's a vital historical figure." On entering the TARDIS, the Doctor bangs his nose on the door; Leela laughs.
- The Doctor has a sub-plasmic beam detector.
- The Doctor tells Leela that knives are for cutting onions.
- At the amphitheatre, the Doctor gives Leela some jelly babies.
- Leela is not familiar with the word "slave".
- The Doctor has heard of the Jezark and calls them "those awful Jezark people".
- The stories in Short Trips: The Muses are inspired by the Muses of Greek mythology. This story is based on Thalia, the Muse of Comedy.