Plutarch, Dion
Bernadotte Perrin, Ed.

14. They therefore no longer abused Dion one by one and secretly, but all together and openly, saying that he was manifestly enchanting and bewitching Dionysius with Plato's doctrines, in order that the tyrant might of his own accord relinquish and give up the power, which Dion would then assume and devolve upon the children of Aristomache, whose uncle he was. And some pretended to be indignant that the Athenians, who in former times had sailed to Sicily with large land and sea forces, but had perished utterly without taking Syracuse, [2] should now, by means of one sophist, overthrow the tyranny of Dionysius, by persuading him to dismiss his ten thousand body-guards, and abandon his four hundred triremes and his ten thousand horsemen and his many times that number of men-at-arms, in order to seek in Academic philosophy for a mysterious good, and make geometry his guide to happiness, surrendering the happiness that was based on dominion and wealth and luxury to Dion and Dion's nephews and nieces.

[3] As a consequence of all this, Dionysius became at first suspicious, and afterwards more openly angry and hostile, and just then a certain letter was secretly brought to him, which Dion had written to the Carthaginian officials, urging them, whenever they should treat with Dionysius for peace, not to hold their interview without including him, since he would help them to arrange everything securely. [4] This letter Dionysius read to Philistus, and after consulting with him, according to Timaeus, he beguiled Dion by a feigned reconciliation. That is, after moderate protestations and a declaration that their quarrel was at an end, he led him off alone beneath the acropolis down to the sea, and then showed him the letter and accused him of conspiring with the Carthaginians against him. [5] And when Dion wished to defend himself, he would not suffer it, but at once placed him, just as he was, on board a small boat, and commanded the sailors in it to set him ashore in Italy.