Plutarch, Dion
Bernadotte Perrin, Ed.

16. As for Plato, Dionysius at once removed him to the acropolis, where he contrived to give him a guard of honour under pretence of hospitable kindness, in order that he might not accompany Dion and bear witness to his wrongs. But after time and intercourse had accustomed Dionysius to tolerate his society and discourse, just as a wild beast learns to have dealings with men, he conceived a passion for him that was worthy of a tyrant, demanding that he alone should have his love returned by Plato and be admired beyond all others, and he was ready to entrust Plato with the administration of the tyranny if only he would not set his friendship for Dion above that which he had for him. [2] Now, this passion of his was a calamity for Plato, for the tyrant was mad with jealousy, as desperate lovers are, and in a short space of time would often be angry with him and as often beg to be reconciled; for he was extravagantly eager to hear his doctrines and share in his philosophical pursuits, but he dreaded the censure of those who tried to divert him from this course as likely to corrupt him.

[3] At this juncture, however, a war broke out, and he sent Plato away, promising him that in the summer he would summon Dion home. This promise, indeed, he immediately broke, but he kept sending to Dion the revenues from his property, and asked Plato to pardon his postponement of the time of Dion's recall, because of the war; as soon as peace was made he would summon Dion home, and he asked him to be quiet, and to attempt no revolution, and to say no evil of him to the Greeks.