Dionysus, son of Zeus, addresses the audience, describing to us how Thebes is his birthplace and is also the ancestral home of his mortal mother, Semele. After Semele's affair with Zeus, his wife, the jealous goddess Hera, taunted the woman for never having known her lover in his true, divine, form. Semele fell for Hera's ploy and begged Zeus to appear to her as a divinity; he came from above as a bolt of lightning, and the mortal Semele, unable to behold him, was burned to death. Zeus rescued the unborn fetus and stitched him into his thigh. Dionysus was not acknowledged by the house of Cadmus, and Semele's family accused her of having a mortal lover and lying about Zeus, dying at his hands as punishment. Dionysus now returns from the East, at last to exact retribution for their disrespectful treatment of his mother's memory and their refusal to permit him to be worshipped or to offer him his sacrificial due. He appears in Thebes in the guise of a male Lydian leader of female bacchants to show the royal family, "even against its will," that he is indeed a god and deserves proper consideration. By the time Dionysus arrives, he has already made mad the women of the palace and driven them to the hills of Mt. Cithaeron, where they, the maenads, sing, dance, and perform bacchic rites. Semele's father, old Cadmus, has turned his kingdom over to his grandson Pentheus. Pentheus violently refuses to worship Dionysus in the face of the bacchanal madness and miracles abounding around him. The prologue ends as Dionysus bids his group of worshippers to take up the drum.
The chorus enters from both sides of the stage, exalting Dionysus. The ode they chant consists of three segments: a)(Prelude): a call for holy silence b)(Hymn in four parts): a declaration of the blessed state of a maenad, a summary of Dionysus's birth, a call to Thebes to worship the Bacchae and a history of the place of the drum in their cult. c)(Epode or refrain): further description of the ecstasy of the bacchants.
Traditionally, the first song or direct address in Greek theater establishes the background and history of the play, clears up any potential confusion and then launches into the story. A prologue also predicts the general outcome and structure of the play, but conceals a few twists and key details. The prologue of The Bacchae recounts material that would have been very familiar to the audiences of the time: the birth, cult and history of Dionysian worship. Euripides, however, is known for his innovations and refinements of classical literary traditions, and he demonstrates this talent through his astute use of the prologue and his recasting of the Dionysian myth.
Instead of using the prologue to merely sketch the main moral of the story, or to establish the pre-eminence of the gods above, dictating human action, Euripides uses the prologue to establish Dionysus as a direct human agent. Dionysus, instead of being only a mysterious, transcendent god, here also appears in mortal form as a character within the drama. Euripides's decision to have Dionysus appear as a mortal is not merely a theatrical device, but is also a comment on the nature of this complex god and that which he represents. Euripides is signaling the central role that disguise and recognition play within the play, and is also pointing to the importance of epiphanies, masks and masking, and shape-changing in the cults and myths of Dionysus. As a god born of a mortal mother, Dionysus comes both from the Olympian heights and the human world; Euripides highlights this by showing him both outside and inside the play. It is appropriate for Dionysus to walk, talk and interact with mortals because of the very communal and intimate emotions brought forth in his worshippers by his power.
Thereby in the prologue Euripides introduces the key to Dionysus' nature: ambiguity. The god not only embodies differences (belief and madness, celebration and destruction) but in his actions demonstrates a similar fluidity. His punishment of Pentheus, for example— which proves excessive, gruesome and terrible—is brought about in an extremely subtle, devious and gradual manner. Finally, the prologue puts the audience in a privileged position by letting it in on Dionysus's secret. None of the other characters in the play know who the Stranger from Lydia really is, and this dramatic irony heightens the sense of unavoidable tragedy in an already powerful play.
In Euripides's time, the extensive use of the chorus had become outmoded, yet Euripides gave the device new life by fusing it with elements from the play itself. The chorus is traditionally a unified singing and dancing body removed from the central actions of the play. Euripides equated these features with the characteristics of the Bacchae, a nomadic cult that worshipped Dionysus through song and dance. The chorus became the Bacchae, and vice-versa. Euripides lets the chorus fulfill its classical function but also gives it a deeper narrative meaning. On the one hand, the chorus comments on the actions of the play, provides a moral voice and links the segments of the play temporally. In The Bacchae, it is also given the role of describing Dionysian rites from within, expressing common reactions, and, most importantly, heightening the drama, hysteria and passion of the play through dance and music. The chorus also serves the function of extolling the more benign, joyful and celebratory side of Dionysus. They are a group of willing devotees of Dionysus that followed the Stranger from the East to Thebes. While their songs are at times bloodthirsty, their actions are not.