It is summer 415.1 Momentously, the Athenian assembly has just taken its decision to sail to Sicily, and the city is busy with preparations. Thucydides continues (6.27):

One night most of the stone Herms in Athens had their faces mutilated. (These are a local feature, with their familiar squarecut figures, and there are many of them both in private porches and in temples.) Nobody knew who had done it; great rewards were offered by the state for information which would help the search, and they passed a further decree offering immunity to anyone, citizen, alien, or slave, who could give information concerning any other impiety. They took the affair more seriously than one might expect: it was taken as an omen for the expedition, and people thought that it sprang from a revolutionary conspiracy to overthrow the democracy.