The god Dionysus delivers the prologue: he has come to Thebes from Asia Minor, bringing his rites, to prove that he is a god and son of Zeus by Semele; all the Theban women are in the woods, frenzied; Pentheus, grandson of Cadmus, rules the city and rejects Dionysus. Dionysus will disguise himself as a man; he summons the chorus of Bacchants (women in Dionysiac frenzy) (1-63). The chorus sings a hymn to Dionysus, telling of his birth, locating the origin of his worship in Crete, and evoking the atmosphere of a Bacchic celebration (64-169). Teiresias, dressed as a bacchant, enters and summons Cadmus, who arrives similarly attired; the two affirm their belief in Dionysus, and prepare to go and join the rites in the woods (170-214). Pentheus enters and establishes himself as the enemy of Dionysus; he has already imprisoned some Bacchants and will do the same to all he catches, even his mother Agave; he says Dionysus is no god, and the women merely use his rites as an excuse to get drunk and have sex (215-248). Seeing Teiresias and Cadmus, he upbraids and threatens them. Teiresias responds with a lengthy defense of the god, touching on the power of wine, including an account of popular error in the myth of his birth, citing his power in prophecy and war, and defending him from the charge of inducing promiscuity. Pentheus is the crazy one, not the Bacchants (249-328). The chorus and Cadmus agree; Cadmus pleads the glory of a god in the family, warning Pentheus not to end up like another scorner of the gods, Actaeon (327-343). Pentheus responds angrily and orders his men to destroy Dionysus' shrine and arrest the Lydian stranger, who is Dionysus in disguise (344-358). Teiresias takes Cadmus off to worship the god and pray that no disaster befall Thebes (359-369). The chorus sings an ode descriptive of the blessings of Dionysus, e.g. freedom from cares; those who are reckless and defy the gods come to a bad end; in Bacchic ecstasy, the chorus longs to journey far away; it ends by celebrating Dionysus, giver of wine and peace, but a hard enemy to those who reject him (370-432).

Pentheus' men enter with the stranger (Dionysus) in chains; they describe how he gave up willingly, but the chained Bacchants broke free as if by magic (433-452). Pentheus admires (mockingly?) the stranger's good looks. Questioned by the king, the stranger says he is a priest of Dionysus from Lydia, and teases the prurient curiosity of Pentheus by refusing to discuss the Dionysian rites. The stranger admits that the god is worshipped at night, but (without actually denying a sexual component to the rites) denies that they encourage debauchery. Pentheus cuts off the stranger's long hair, seizes his thyrsus (willow wand), and has him clapped in irons (453-515). Dionysus goes along, but promises vengeance. The chorus sings an ode, starting with a celebration of the birth of Dionysus by the river Dirce; Pentheus' wildness is attributed to his descent from the Theban dragon, and the chorus prays Dionysus to destroy him. Where is Dionysus? The chorus sings of his favourite haunts (515-575). Thunder pounds and lightning flashes; the palace of Pentheus collapses in an earthquake, as Dionysus shouts to his worshippers, the chorus (576-595). Dionysus emerges triumphant from the rubble, and describes how he deluded Pentheus, making him chain a bull in the stable and stab a phantom, thinking that he chained and stabbed the stranger (596-642). Pentheus comes out, still blustering at the god; their exchange is interrupted by a messenger, a cowherd who has observed the maenads in action and promises a strange tale (643-677). The tale: the Bacchants, including the royal women of Thebes, awoke from a chaste sleep; miracles, such as water springing from a rock and wild beasts suckling at women, illustrated their oneness with nature; the shepherd and his friends hid in the woods to ambush the women and catch them for Pentheus, but were driven off by the bacchants, who proceeded to rip apart the cattle with their bare hands. The maenads then sacked a village, easily defeating the armed men who opposed them. The messenger ends by suggesting that Pentheus recognize Dionysus, who is as elemental as Aphrodite (678-775). Pentheus tries to mobilize his army, but Dionysus counters by offering to return the women peacefully to the city; when Pentheus refuses, Dionysus suggests that he might like to observe the maenads (776-811). Pentheus, imagining an orgy in the modern sense, is eager. Dionysus suggests that the best way to do this is for Pentheus to disguise himself as a woman; Pentheus is upset at the idea, but agrees to consider it and exits (812-846). Dionysus hints to the chorus of Pentheus' coming doom, and prays to himself to cloud Pentheus' mind (846-861). The chorus sings an ode, longing to run wild and free again; beating an enemy is good; divine vengeance is slow but sure (862-911).

Dionysus returns with Pentheus in drag; Pentheus is zoned out and hallucinating. Dionysus toys with him in seriocomic wise, sending him off to spy on the bacchants with ironic remarks about how his mother Agave will carry him home (912-976). The chorus sings savagely of the vengeance to be taken upon the intruder; there is philosophical speculation on the nature of humility, and more bloodthirsty longings (977-1021). A messenger arrives to tell the chorus that Pentheus is dead; they react with glee. The messenger describes how Pentheus, in the woods, climbed a tree so as to see the women better; then Dionysus called on his maenads, and they came after Pentheus; failing to dislodge him from the tree with missiles, they ripped down the tree and tore the king apart. In the lead was his mother Agave, so much in the grip of frenzy that she ignored his cries of 'mother'. Agave is returning with the head of Pentheus on a stick; she thinks he was a lion (1022-1152). The chorus celebrates the event. Agave enters, breathless and triumphant, and boasts to the chorus of the success of the women in the hunt. Cadmus arrives with the pieces of Pentheus' body; Agave asks his praise for her achievement, and he responds with lamentation (1153-1251). In tense stichomythy, Agave comes out of her trance and recognizes the head of Pentheus; it is revealed that she once shared his attitude, and the punishment is hers as much as his. Cadmus laments the death of Pentheus and interprets the whole as evidence of divine power (1252-1329). Agave laments over the mangled corpse of her son; Dionysus appears as deus ex machina and explains what he has wrought; all of Thebes will suffer for what Pentheus has done; Agave and her sisters will go into exile. [The lacuna, or gap in our manuscripts, comes at this point]. Cadmus and his wife Harmonia will be changed into snakes and lead a barbarian army against Greeks before ending up in the isles of the blessed. Appeals to Dionysus are in vain, and the play ends in lamentation (1330-1395).