Cleomenes wanted revenge, so he made a deal with Leotychides son of Menares son of Agis, of the same family as Demaratus. The deal was that Leotychides would go with Cleomenes against the Aeginetans if he became king.

Leotychides had already become strongly hostile to Demaratus for the following reason: Leotychides was betrothed to Percalus, daughter of Demarmenus, but Demaratus plotted and robbed him of his marriage, stealing Percalus and marrying her first.

From this affair Leotychides was hostile toward Demaratus, so at Cleomenes' instigation he took an oath against him, saying that he was not king of the Spartans by right, since he was not Ariston's son. After making this oath, he prosecuted him, recalling that utterance which Ariston had made when the servant told him he had a son, and he counted up the months and swore that it was not his.

Taking his stand on this remark, Leotychides declared that Demaratus was not Ariston's son and that he was not rightly king of Sparta [22.4417,37.0667] (Perseus) Sparta, bringing as witnesses the ephors who had been sitting beside Ariston and heard him say this.