Menaechmi, a Latin-language play, is often considered Plautus' greatest play. The title is sometimes translated as The Brothers Menaechmus or The Two Menaechmuses.

Menaechmi is a comedy about mistaken identity, involving a set of twins, Menaechmus of Epidamnus and Menaechmus of Syracuse. It incorporates various Roman stock characters including the parasite, the comic courtesan, the comic slave, the domineering wife, the doddering father-in-law and the quack doctor. As with most of Plautus' plays, much of the dialogue was sung.Paul L. MacKendrick, Herbert M. Howe, Classics in Translation, Volume II,1959, "" May 11, 2011

The play is set in a street in Epidamnus,Modern Durrës a city on the coast of what is now Albania. Facing the audience are two houses, that of Menaechmus I and that of Erotium, the prostitute he is courting.

Plot Prologue: Moschus has twin sons, Menaechmus and Sosicles. Moschus decides to take only one of the twins, Menaechmus, with him on a business trip, while the twins are still young. During the trip, Menaechmus is abducted and adopted by a businessman who lives in Epidamnus, separating the twins. Their father dies of sorrow and their grandfather changes Sosicles' name to Menaechmus (i.e., Menaechmus of Syracuse). When the twins are grown to manhood, Menaechmus of Syracuse sets out in search of his brother. He arrives in Epidamnus, unaware that his twin brother is there also.

Act 1: Here, the brother is first shown to be, with good cause, the despair of his jealous wife. He is seen leaving his house, berating his spouse as a shrew and a harpy, promising that she shall have good cause for her jealousy. He confides to Peniculus, a professional parasite, that he has stolen his wife's mantle and is going to give it to Erotium, a prostitute who lives next door.

The two go to Erotium's door, and the husband presents the mantle with many blandishments. He suggests that a fitting return would include a dinner for himself and Peniculus. Erotium agrees, and the two men go to the Forum for preliminary drinks while the meal is being prepared.

Act 2: Meanwhile, the twin from Syracuse has arrived with Messenio, his slave. The latter warns him of the depravity of Epidamnus, urging an end to the search for his missing brother since their money is nearly gone. His master gives his purse for safekeeping to the slave who continues his warning against the cunning people of Epidamnus "who think nothing of accosting a stranger" and bilking him of his money, when Erotium steps out of her house and endearingly accosts the Syracuse Menaechmus, thinking him to be his brother.

She asks why he hesitates to enter when dinner is ready, and the confused twin asks her, quite formally, what business he has with her. Why, the business of Venus, Erotium replies coyly. Messenio whispers to his master that the lady undoubtedly is a schemer for his money, and asks her if she knows his master. He is Menaechmus, of course, replies Erotium. This amazes the twin, but Messenio explains that spies of the city's thieves probably have learned his name.

Erotium, tiring of what she considers foolery, tells Menaechmus to come into dinner and bring Peniculus. Peniculus, he answers, is in his baggage—and what dinner is she talking about? The dinner he ordered when he presented his wife's mantle, she replies. He first protests vainly that he hasn't any wife and has just arrived in the city, then begins to realize the possibilities of a dinner and a pretty girl. He sends Messenio to the inn, giving him orders to return for his master at sunset.

Act 3: After the meal, he leaves his house with a garland on his head and the mantle over his arm; Erotium has told him to have it re-trimmed. He is chuckling over his luck—dinner, kisses and an expensive mantle—all for nothing, when the irate Peniculus, who has lost the Epidamnus twin in the Forum crowd, meets him and berates him for dining before he could arrive. Quite naturally treated as a stranger, Peniculus angrily rushes to tell the other twin's wife of the stolen mantle.

The Syracuse brother, further baffled because the unknown Peniculus addressed him by his name, is pinching his ear to make sure that he is awake when Erotium's maid comes out and hands him a bracelet to be taken to a goldsmith for repair. He suspects that something is amiss, and hurries off to the inn to tell Messenio of the happy shower of valuables that has been raining upon him.

Act 4: Now the furious wife, told by Peniculus of her man's trick, rushes out of her house just in time to meet her husband returning from the Forum, expecting Erotium's banquet. She tells him to return the mantle or stay out of her house, and the husband goes to Erotium to get it, resolving to buy his sweetheart a better one. He is stupefied when she declares him a liar and a cheat, and tells him that she has already given him both the mantle and her bracelet. So the Epidamnus twin finds the doors of both his wife and mistress slammed in his puzzled face, and goes off to get the counsel of his friends.

The Syracuse Menaechmus returns, the mantle still over his arm, in search of Messenio, who has left the inn. His brother's wife sees him, and assuming him to be her husband, demands that he confess his shame. He asks her of what he should be ashamed—and, furthermore, why she should address a total stranger so. He adds that he didn't steal her mantle, that a lady gave it to him. This is too much for the wife, who calls her father from the house. The father, also assuming that he is the husband, tells him that he must be crazy. This idea seems an excellent means of escape for Menaechmus: he feigns insanity so violently that the father rushes off for a physician, the wife seeks safety in the house, and Menaechmus goes off to resume his hunt for Messenio.

Act 5: As the father comes back with a doctor, the real husband returns. He flies into a rage when his wife and father-in-law add to his troubles by implying that he is quite mad. His anger convinces the doctor of his insanity, and he summons slaves to bind him and take him to an asylum. Just then, Messenio appears, and, thinking the struggling husband his master, overpowers the slave. As a reward he asks for his own freedom. The husband tells Messenio that he doesn't know him, but by all means to consider himself freed; then he begins to suspect he may really be a bit crazy when Messenio tells him that he will return shortly to give him the money he has been safeguarding. Husband Menaechmus is not too addled, however, to profess his ownership of the purse.

The husband goes to Erotium's house in further search of the mantle. The Syracuse twin returns, in his quest of Messenio, at the moment when the servant hurries back with his purse. His master upbraids him for having been gone so long, but the slave protests that he has just saved his owner from ruffians and has been set free. The master is pondering this new muddle when his twin appears from Erotium's house.

The two brothers rub their eyes in bewilderment on seeing each other, but explanations quickly bring recognition. They embrace. The happy master truly sets the slave free, and the brothers decide that the first Menaechmus shall go to live with his twin in Syracuse. Messenio announces an auction in the morning of the husband's goods, everything to go to the block—even the wife, if there be a buyer.

Metrical scheme

Plautus's plays are traditionally divided into five acts; these are referred to below for convenience, since many editions make use of them. However, it is not thought that they go back to Plautus's time, since no manuscript contains them before the 15th century.Merrill, F. R. (1972). Titi Macci Plauti Mostellaria, p. xix. Also, the acts themselves do not always match the structure of the plays, which is more clearly shown by the variation in metres.

In Plautus's plays the usual pattern is to begin each section with iambic senarii (which were spoken without music), then a scene of music in various metres, and finally a scene in trochaic septenarii, which were apparently recited to the accompaniment of (a pair of reed pipes). Moore calls this the "ABC succession", where A = iambic senarii, B = other metres, C = trochaic septenarii.Moore, Timothy J. (2012), Music in Roman Comedy. Cambridge University Press, pp. 237-42, 253-8, 305-8, 367-71. However, the ABC order is sometimes varied.

If the A passages (iambic senarii) are taken as starting a section, and the C passages (trochaic septenarii) are taken as ending it, in this play the order of the metrical sections is as follows:Marshall, C. W. (2006). The Stagecraft of Roman Comedy (Cambridge University Press), p. 210.

Alternatively, following Moore,T. J. Moore (2012), Music in Roman Comedy, pp. 238–240. the sections could be taken as following the two brothers in turn as follows:

In first section there are two "B" passages, the first polymetric and the second in mixed iambo-trochaic metres.

Timothy Moore points out that each time Menaechmus I enters the stage, he is accompanied by music; but throughout almost the whole play each entrance of Menaechmus II coincides with iambic senarii, which were unaccompanied. This no doubt helped the audience to distinguish one brother from the other, if they were identically dressed.T. J. Moore (2012), Music in Roman Comedy, p. 258.

Prologue Prologue (lines 1–76): ia6 (76 lines) An actor explains how a merchant in Syracuse in Sicily had twin sons. One of them, on a visit to Tarentum, became separated from his father and was abducted to Epidamnus by a rich childless man, who later drowned in a river, bequeathing his property to the boy. In memory of the lost boy, the grandfather meanwhile renamed the other twin by the same name as the lost one. This second twin has now come to Epidamnus to make enquiry about his brother.

Menaechmus I arranges dinner Act 1.1 (77–109): ia6 (33 lines) A parasite, Peniculus (the name means a sponge used for wiping tables) is waiting outside Menaechmus's house in the hope of an invitation to dinner. Act 1.2 (110–119): polymetric song (25 lines) The young man Menaechmus emerges quarrelling with his wife through the door, threatening to divorce her if she continues nagging. Act 1.2 (119–134): mixed iambic and trochaic metres (16 lines) He says she is spoiled (tr8), and lists all the presents he buys her (ia4). He threatens to dine with a prostitute instead of her (tr7). Then he tells the audience that he has stolen his wife's cloak as a present for his girlfriend. Act 1.2–1.4 (135–225): tr7 (87 lines) The one-eyed Peniculus accosts Menaechmus and exchanges banter, still hoping to get a dinner. They approach the door of Erotium, the prostitute, and knock. Erotium comes out and there is more banter. Menaechmus gives her the cloak, and asks her to prepare dinner for all of them; meanwhile he and Peniculus will go to the market to get a drink. When they have gone, Erotium calls out her cook Cylindrus and orders him to go to buy some food for dinner.

Menaechmus II eats the dinner Act 2.1–2.2 (226–350): ia6 (124 lines) Menaechmus II now enters the street, along with his prudent slave Messenio, who advises him that after six years searching for news of his brother all over the Mediterranean, their purse is almost empty. He warns him to watch his money since Epidamnus is full of voluptuaries, drinkers, tricksters, conmen, and the most charming prostitutes in the world. Menaechmus asks for the purse for safekeeping, which Messenio gives to him. – They now meet Cylindrus the cook, who addresses Menaechmus by name: each thinks the other is mad, but Messenio warns that he is probably a conman. Act 2.3 (351–368): song mostly anapaests and some iambs (18 lines) The prostitute Erotium comes out from her house. She gives instructions to her staff, then welcomes Menaechmus II and invites him in. Act 2.3–3.1 (369–465): tr7 (93 lines)