The play was produced in 405 BCE, when Athens was on the brink of total defeat by Sparta, and had suffered coups and tyranny, as the Peloponnesian War dragged on for decades. Three great poets (playwrights) Euripides, Sophocles, and Agathon had recently died. In this ruined air, Aristophanes created his brilliantly funny play about Dionysus' search for a poet to take back out of Hades to save Athens. The Frogs not only won first prize, it was awarded the extraordinary honour of a repeat performance.

Dionysus was the god at whose festivals plays were performed. So when there are no more good poets left to write them, he becomes desperate. He decides to disguise himself as the great hero Heracles to cover up the fact of being a coward, and go to Hades to seek them. He turns up at the real Heracles' house to ask his advice.

The play opens with Dionysus and his servant Xanthias, who is heavily burdened, and is a typical comic servant in complaining about his load. They begin by surveying the audience and discussing the complaining-servant jokes they could start with; Xanthias offers a few, but Dionysus is sick of hearing them all from bad playwrights.

Heracles tells them of the routes down into the underworld. Then a funeral procession conveniently passes by, and Dionysus stops the corpse to ask whether he could hitch a lift. The corpse says that'll be two drachmas, cash. Dionysus counts his change and says he can offer nine obols. The disgusted corpse says "I'd rather live!" (Anabioiên nun palin) and leaves. Xanthias tut-tuts at this and says "He'll come to a bad end".

So they continue walking in the stygian gloom and get to the lake, where Charon arrives and takes Dionysus on board. By the way, Tom Stoppard in his The Invention of Love trades on this scene, and has a similarly comic cab-driver of a Charon say to A.E. Housman, "I had that Dionysus in the back of my boat". Charon orders Dionysus to take the oars, and Dionysus struggles with great difficulty through a marsh, full of the chorus, now revealed...the frogs.

Brekekekex, koax, koax,
Koax, koax, koax!

Oh we are the musical Frogs!
We live in the marshes and bogs!
Sweet, sweet is the hymn
That we sing as we swim,
And our voices are known
For their beautiful tone

Translation by David Barrett, 1964, Penguin

The frogs and Dionysus alternate verses, they singing how none can surpass them for harmony and tone, he moaning about the blisters on his bum, all interlarded with the famous croaking brekekekex koax koax.

Arriving on the other side, they proceed with increasing terror. There is some farce because he is still dressed as Heracles, who got into trouble with the mistress but was very friendly indeed with the maid. Swapping costumes with Xanthias leads to further confusion and arrest, and Dionysus insists that he is a god and Xanthias his mortal slave. Xanthias proposes whipping them both to see who cracks first.

In the palace of Pluto and Persephone there is a throne of honour for the greatest tragedian. For fifty years Aeschylus has occupied it, but the newly-dead Euripides has now claimed it, and Dionysus is brought in to judge the issue. (This involves complicated measuring apparatus.) Aeschylus, old-fashioned, portentous, moral, and grandiose, says that in the matter of quoting texts he is at a disadvantage because all his have outlived him so he doesn't have them to hand. Euripides is realistic, subtle, colloquial, and a-moral. They quote their lines at each other and argue about them, including parodying each other's style. Aeschylus says Euripides' is just jingly, and shows this by adding "lost his bottle of oil" to any grand line Euripides begins.

The play ends with a plea for the return from exile of the brilliant and untrustworthy Alcibiades, probably the only commander who could save Athens. Dionysus chooses Aeschylus to return with him and the chorus sing

Spirits of the darkness,
Speed him on his way,
Safely may he journey
To the light of day.

To the City's counsels
May he wisdom lend;
Then of war and suffering
There shall be an end.