In 366 BCE, Dionysius II became tyrant of Syracuse, and his uncle Dion advised him to invite Plato to come to Sicily. The Athenian philosopher might be a worthy adviser, he thought. The results, however, were catastrophic, because other courtiers feared Dion's influence and accused him of high treason, for which they could indeed produce some (fake?) evidence. Dion was sent into exile and the advice of the philosopher, now without protector, was ignored. Plato was forced to leave Sicily.
In his seventh letter, here offered in the translation by J. Harward, Plato tells about his adventures. There is some discussion about the authorship - several classicists have argued that this text was not written by Plato himself - but the events described seem to be authentic.
Plato on Sicily
I sailed from home [...] principally through a feeling of shame with regard to myself, lest I might some day appear to myself wholly and solely a mere man of words, one who would never of his own will lay his hand to any act. Also there was reason to think that I should be betraying first and foremost my friendship and comradeship with Dion, who in very truth was in a position of considerable danger. If therefore anything should happen to him, or if he were banished by Dionysius and his other enemies and coming to us as exile addressed this question to me: "Plato, I have come to you as a fugitive, not for want of soldiers, nor because I had no cavalry for defense against my enemies, but for want of words and power of persuasion, which I knew to be a special gift of yours, enabling you to lead young men into the path of goodness and justice, and to establish in every case relations of friendship and comradeship among them. It is for the want of this assistance on your part that I have left Syracuse and am here now. And the disgrace attaching to your treatment of me is a small matter. But philosophy -whose praises you are always singing, while you say she is held in dishonor by the rest of mankind -must we not say that philosophy along with me has now been betrayed, so far as your action was concerned? Had I been living at Megara,note[A town near Athens.] you would certainly have come to give me your aid towards the objects for which I asked it; or you would have thought yourself the most contemptible of mankind. But as it is, do you think that you will escape the reputation of cowardice by making excuses about the distance of the journey, the length of the sea voyage, and the amount of labor involved? Far from it."
To reproaches of this kind what creditable reply could I have made? Surely none.
I took my departure, therefore, acting, so far as a man can act, in obedience to reason and justice, and for these reasons leaving my own occupations, which were certainly not discreditable ones, to put myself under a tyranny which did not seem likely to harmonize with my teaching or with myself. By my departure I secured my own freedom from the displeasure of Zeus Xenios, and made myself clear of any charge on the part of philosophy, which would have been exposed to detraction, if any disgrace had come upon me for faint-heartedness and cowardice.
On my arrival, to cut a long story short, I found the court of Dionysius full of intrigues and of attempts to create in the sovereign ill-feeling against Dion. I combated these as far as I could, but with very little success; and in the fourth month or thereabouts, charging Dion with conspiracy to seize the throne, Dionysius put him on board a small boat and expelled him from Syracuse with ignominy.
All of us who were Dion's friends were afraid that he might take vengeance on one or other of us as an accomplice in Dion's conspiracy. (With regard to me, there was even a rumor current in Syracuse that I had been put to death by Dionysius as the cause of all that had occurred.) Perceiving that we were all in this state of mind and apprehending that our fears might lead to some serious consequence, he now tried to win all of us over by kindness: me in particular he encouraged, bidding me be of good cheer and entreating me on all grounds to remain. For my flight from him was not likely to redound to his credit, but my staying might do so. Therefore, he made a great pretense of entreating me. And we know that the entreaties of sovereigns are mixed with compulsion.
So to secure his object he proceeded to render my departure impossible, bringing me into the acropolis, and establishing me in quarters from which not a single ship's captain would have taken me away against the will of Dionysius, nor indeed without a special messenger sent by him to order my removal. Nor was there a single merchant, or a single official in charge of points of departure from the country, who would have allowed me to depart unaccompanied, and would not have promptly seized me and taken me back to Dionysius, especially since a statement had now been circulated contradicting the previous rumors and giving out that Dionysius was becoming extraordinarily attached to Plato.
What were the facts about this attachment? I must tell the truth. As time went on, and as intercourse made him acquainted with my disposition and character, he did become more and more attached to me, and wished me to praise him more than I praised Dion, and to look upon him as more specially my friend than Dion, and he was extraordinarily eager about this sort of thing. But when confronted with the one way in which this might have been done, if it was to be done at all, he shrank from coming into close and intimate relations with me as a pupil and listener to my discourses on philosophy, fearing the danger suggested by mischief-makers, that he might be ensnared, and so Dion would prove to have accomplished all his object. I endured all this patiently, retaining the purpose with which I had come and the hope that he might come to desire the philosophic life. But his resistance prevailed against me.
The time of my first visit to Sicily and my stay there was taken up with all these incidents.