Plutarch, Themistocles
Bernadotte Perrin, Ed.

After he had been thus banished from the city, and while he was sojourning at Argos, circumstances connected with the death of Pausanias gave his enemies at Athens ground for proceeding against him. The one who actually brought in the indictment against him for treason was Leobotes the son of Alcmeon, of the deme Agraule, but the Spartans supported him in the accusation. Pausanias, while engaged in his grand scheme of treachery, at first kept it concealed from Themistocles; [2] but when he saw him thus banished from his state and in great bitterness of spirit, he made bold to invite him into partnership in his own undertakings, showing him a letter he had received from the king, and inciting him against the Hellenes as a base and thankless people. Themistocles rejected the solicitation of Pausanias, and utterly refused the proffered partnership; and yet he disclosed the propositions to no one, nor did he even give information of the treacherous scheme, because he expected either that Pausanias would give it up of his own accord, or that in some other way he would be found out, since he was so irrationally grasping after such strange and desperate objects. [3]

And so it was that, when Pausanias had been put to death, certain letters and documents regarding these matters were discovered which cast suspicion on Themistocles. The Lacedaemonians cried him down, and his envious fellow-citizens denounced him, though he was not present to plead his cause, but defended himself in writing, making particular use of earlier accusations brought against him. [4] Since he was once slanderously accused by his enemies before his fellow-citizens—so he wrote, as one who ever sought to rule, but had no natural bent nor even the desire to be ruled, he could never have sold himself with Hellas to Barbarians, much less to foemen. The people, however, were over-persuaded by his accusers, and sent men with orders to arrest him and bring him up in custody to stand trial before a Congress of Hellenes.