Young scribe Marcus falls for new neighbor Cynthia. Marcus' roommate Stylax is anxious for them to respond to an invitation to an orgy.

The boys are introduced to Cynthia's new boyfriend Cassius. Stylax plays a prank on Aurelius.

Stylax buys Grumio an erotic vase for his birthday featuring a character who bears a striking resemblance to someone nearby. Marcus has done nothing for his slave and, under pressure from the girls, suggests they swap roles for the day. Stylax hangs out with his cousin Lucretia, with whom he has an unusually close relationship.

To endear himself to Cynthia, Marcus befriends a stray cat she rescued from the courtyard. Stylax visits a sexual health clinic where he falls for a nurse.

Mass immigration from Thrace puts the boys into contact with a sexy Thracian named Irina and a dazzling yellow exotic fruit, the banana. Meanwhile, Marcus has an unfortunate encounter with an elderly war veteran.

Marcus hopes to use Saturnalia to make his move on Cynthia. Grumio has a close call with a priest who wants to ship him off to Cyprus as a castrati.