Plutarch Pyrrhus 5

[1] After this marriage he was held in still greater esteem, and since Antigone was an excellent wife to him, he brought it to pass that he was sent into Epeirus with money and an army to regain his kingdom. Most people there were glad to see him come, owing to their hatred of Neoptolemus, who was a stern and arbitrary ruler. However, fearing lest Neoptolemus should have recourse to one of the other kings, he came to terms and made friendship with him on the basis of a joint exercise of tile royal power.

[2] But as time went on there were people who secretly exasperated them against one another and filled them with mutual suspicions. The chief ground, however, for action On the part of Pyrrhus is said to have had its origin as follows.
  It was customary for the kings, after sacrificing to Zeus Areius at Passaro, a place in the Molossian land, to exchange solemn oaths with the Epeirots, the kings swearing to rule according to the laws, and the people to maintain the kingdom according to the laws.

[3] Accordingly, this was now done; both the kings were present, and associated with one another, together with their friends, and many gifts were interchanged. Here Gelon, a man devoted to Neoptolemus, greeted Pyrrhus in a friendly manner and made him a present of two yoke of oxen for ploughing. Pyrrhus was asked for these by Myrtilus, his cup-bearer; and when Pyrrhus would not give them to him, but gave them to another, Myrtilus was deeply resentful.

[4] This did not escape the notice of Gelon, who therefore invited Myrtilus to supper, and even, as some say, enjoyed his youthful beauty as they drank; then he reasoned with him and urged him to become an adherent of Neoptolemus and to destroy Pyrrhus by poison. Myrtilus accepted the proposal, pretending to approve of it and to be persuaded, but informed Pyrrhus. He also, by the king’s orders, presented Alexicrates, the king’s chief cup-bearer, to Gelon, assuring him that he would take part in their enterprise; for Pyrrhus wished to have several persons who could testify to the intended crime.

[5] Thus Gelon was thoroughly deceived, and Neoptolemus as well, and as thoroughly, who, supposing that the plot was duly progressing, could not keep it to himself, but in his joy would talk about it to his friends. Once, in particular, after a revel at the house of his sister Cadmeia, he fell to prattling about the matter, supposing that no one would hear the conversation but themselves; for no one else was near except Phaenarete, the wife of Samon, a man who managed the flocks and herds of Neoptolemus, and Phaenarete was lying on a couch with her face to the wall and seemed to be asleep.

[6] But she heard everything, and next day went unobserved to Antigone the wife of Pyrrhus, and told her all that she had heard Neoptolemus say to his sister. When Pyrrhus learned of it, he kept quiet for a time, but on a day of sacrifice invited Neoptolemus to supper and killed him.

[7] For he was aware that the chief men among the Epeirots were devoted to himself and were eager to see him rid himself of Neoptolemus; also that they wished him not to content himself with having a small share of the kingdom, but to follow his natural bent and attempt greater things, and, now that some suspicion had added its weight to other motives for the deed, to anticipate Neoptolemus by taking him off first.