History of the Peloponnesian War

They persuade some few of the men in the island, by secretly sending friends to them, and instructing them to say, as though with a kind motive, that it was best for them to make their escape as quickly as possible, and that they would themselves get a vessel ready, for that the Athenian generals intended to give them up to the Corcyraean populace.

So when they had persuaded them, and through their own arrangements about the vessel the men were caught sailing away, the treaty was declared void, and the whole party given up to the Corcyraeans.