Dionysus, son of Zeus and the mortal Semele, has come to Thebes with his followers, the Bassarids. King Pentheus fears the inner freedom and eroticism which Dionysus propagates and which the king represses in himself. The citizens of Thebes leave the city to greet Dionysus and Tiresias soon follows them .to Mount Cytheron. After a Captain of the Royal Guard reads Pentheus’ proclamation forbidding anybody to believe that Zeus had a son by Semele, Pentheus extinguishes the flame on Semele’s tomb.

Agave and Autonoe, however, follow the call of the god. Cadmus urges Pentheus to reconsider his proclamation, but the king orders the arrest of those on Mount Cytheron. Alone with Beroe, Pentheus confesses that he is horrified by the shameless rites of Dionysus and takes a vow of abstinence.

The prisoners are brought in and among them are Agave, Autonoe, Tiresias and Dionysus, disguised as a stranger. Pentheus demands that they reveal the whereabouts of Dionysus, but no one answers. Beroe recognizes the stranger and tries to warn Pentheus. The king orders Tiresias banished, and Agave and Autonoe imprisoned in the palace. He then questions the stranger who, after making elusive replies, is led away to be tortured.

During an earthquake, the flame on Semele’s tomb reappears. The prisoners escape and rush back to Mount Cytheron while Dionysus returns to confront Pentheus. He induces the king to look into his mother’s mirror. Pentheus sees his own repressed fantasies in an erotic vision involving Agave, Autonoe and the Captain of the Royal Guard. He decides to go to Mount Cytheron to see for himself. Dionysus advises him to go disguised as a woman to avoid being recognized, and Pentheus, dressed in his mother’s gown, is escorted by Dionysus to Mount Cytheron.

On Mount Cytheron the Maenads discover Pentheus spying in their midst and in their frenzy tear him limb from limb. The celebrants return from Cytheron to the palace. Among them is Agave, who led the debacle and tore Pentheus’ head from his neck. She collapses after she is finally made to realize the terrible crime she has committed. The Bassarids disclaim any share in the guilt. Triumphant in his revenge, Dionysus banishes Cadmus and his family from Thebes and has the guards set fire to the palace. He then calls upon Semele to join him on Olympus. The Bassarids rejoice in the triumph of freedom.