The Knights (Ancient Greek: Ἱππεῖς Hippeîs; Attic: Ἱππῆς) was the fourth play written by Aristophanes, who is considered the master of an ancient form of drama known as Old Comedy. The play is a satire on the social and political life of classical Athens during the Peloponnesian War and in this respect it is typical of all the dramatist's early plays. It is unique however in the relatively small number of its characters and this was due to its scurrilous preoccupation with one man, the pro-war populist Cleon. Cleon had prosecuted Aristophanes for slandering the polis with an earlier play, The Babylonians (426 BC), for which the young dramatist had promised revenge in The Acharnians (425 BC), and it was in The Knights (424 BC) that his revenge was exacted. The Knights won first prize at the Lenaia festival when it was produced in 424 BC.
The Knights is a satire on political and social life in 5th-century BC Athens, the characters are drawn from real life and Cleon is clearly intended to be the villain. However it is also an allegory, the characters are figures of fantasy and the villain in this context is Paphlagonian, a comic monstrosity responsible for almost everything that's wrong with the world. The identity Cleon=Paphlagonian is awkward and the ambiguities aren't easily resolved. This summary features the real-world names Cleon, Nicias and Demosthenes (though these names are never mentioned in the play). See Discussion for an overview of the ambiguous use of characterization in The Knights.
Short summary: A sausage seller, Agoracritus, vies with Cleon for the confidence and approval of Demos ('The People' in Greek), an elderly man who symbolizes the Athenian citizenry. Agoracritus emerges triumphant from a series of contests and he restores Demos to his former glory.
Detailed summary: Nicias and Demosthenes run from a house in Athens, complaining of a beating that they have just received from their master, Demos, and cursing their fellow slave, Cleon, as the cause of their troubles. They inform the audience that Cleon has wheedled his way into Demos's confidence and they accuse him of misusing his privileged position for the purpose of extortion and corruption. They advise us that even the mask-makers are afraid of Cleon and not one of them could be persuaded to make a caricature of him for this play. They assure us however that we are clever enough to recognize him even without a mask. Having no idea how to solve their problems, they pilfer some wine from the house, the taste of which inspires them to an even bolder theft – a set of oracles that Cleon has always refused to let anyone else see. On reading these stolen oracles, they learn that Cleon is one of several peddlers destined to rule the polis and that it is his fate to be replaced by a sausage seller. As chance would have it, a sausage seller passes by at that very moment, carrying a portable kitchen. Demosthenes informs him of his destiny. The sausage seller is not convinced at first but Demosthenes points out the myriads of people in the theatre and he assures him that his skills with sausages are all that is needed to govern them. Cleon's suspicions meanwhile have been aroused and he rushes from the house in search of trouble. He immediately finds an empty wine bowl and he loudly accuses the others of treason. Demosthenes calls upon the knights of Athens for assistance and a Chorus of them charges into the theatre. They converge on Cleon in military formation under instructions from their leader:
Cleon is given rough handling and the Chorus leader accuses him of manipulating the political and legal system for personal gain. Cleon bellows to the audience for help and the Chorus urges the sausage-seller to outshout him. There follows a shouting match between Cleon and the sausage seller with vulgar boasts and vainglorious threats on both sides as each man strives to demonstrate that he is a more shameless and unscrupulous orator than the other. The knights proclaim the sausage-seller the winner of the argument and Cleon then rushes off to the Boule to denounce them all on a trumped-up charge of treason. The sausage seller sets off in pursuit and the action pauses for a parabasis, during which the Chorus steps forward to address the audience on behalf of the author.