The play opens with a Prologue, spoken by the Chief Actor of the company. Alongside establishing the tone for the comedy–fast-paced, playful and metatheatrical–the Prologue gives the backstory to the play. It explains that a merchant from Syracuse, named Moschus, went to market at Tarentum with one of his identical twin sons, Menaechmus. The young boy got lost in the crowd and was whisked away by a merchant from Epidamnus. Moschus was so distraught that he died, while the boys’ grandfather renamed the surviving twin Menaechmus (written, in the play, as Menaechmus II).

Having explained the background, the Prologue then reveals the time and place of the play itself. The setting is Epidamnus, in Greece, on a street which passes Menaechmus’s house on the way from the harbor to the forum. Several years have elapsed: Menaechmus is now very rich and married to a “dowried female” (61); Menaechmus II is just about to arrive in Epidamnus, as part of a long voyage in search of his brother.

After the Prologue, the first character to enter the stage is Peniculus, the parasite. With a name literally meaning “sponge,” Peniculus is a stock character from Roman comedy, a hanger-on or flatterer who attaches himself to a richer man in order to get free food and advantages, in return for running errands and fawning on his provider.