Plutarch, Dion
Bernadotte Perrin, Ed.

54. Now, there was a certain comrade of Dion's named Callippus, an Athenian, who, as Plato says,¹ had become intimately acquainted with him, not as a fellow pupil in philosophy, but in consequence of initiation into the mysteries and the recurrent comradeship which this brought. He took part in Dion's expedition and was held in honour by him, so that he even entered Syracuse with him at the head of all his comrades, with a garland on his head, after winning glorious distinction in battle. [2] But now that the chief and noblest friends of Dion had been consumed away by the war, and Heracleides was dead, he saw that the people of Syracuse were without a leader, and that he himself was very much in favour with Dion's soldiers. Therefore, showing himself the vilest of men, and altogether expecting that he would have Sicily as a reward for murdering his friend, and, as some say, having received twenty talents from the enemy to pay him for doing the murder, he bribed some of Dion's mercenaries into a conspiracy against him, beginning his work in a most malicious and rascally manner. [3] For he was always reporting to Dion various speeches of his soldiers against him, either actually uttered or fabricated by himself, and in this way won his confidence, and was authorized to meet secretly with whom he would and talk freely with them against Dion, in order that no lurking malcontents might remain undiscovered. [4] By this means Callippus succeeded in quickly discovering and banding together the evil-minded and discontented citizens, and, whenever any one who had repulsed his overtures told Dion about them, Dion was not disturbed nor vexed, but assumed that Callippus was merely carrying out his injunctions.