Phaedromus is in love with Planesium, a slave girl belonging to the pimp Cappadox.
Phaedromus sends Curculio to borrow money.
Unsuccessful, Curculio happens to run into Therapontigonus, a soldier who intends to purchase Planesium.
After Curculio learns of his plans, he steals the soldier’s ring and returns to Phaedromus.
They fake a letter and seal it using the ring.
Curculio takes it to the soldier’s banker Lyco, tricking him into thinking he was sent by Therapontigonus.
Lyco pays Cappadox, under the conditions that the money is to be returned if it is later discovered that she is freeborn.
Curculio takes the girl back to Phaedromus.
When the trick is discovered, angry Therapontigonus confronts the others.
Planesium discovers from the ring that she is actually Therapontigonus’s sister.
Since she is freeborn, Therapontigonus is returned his money, and Planesium is allowed to marry Phaedromus.