Plutarch Aratus 5

[1] The first to whom he imparted his design were Aristomachus and Ecdelus. Of these, the one was an exile from Sicyon, and Ecdelus was an Arcadian of Megalopolis, a student of philosophy and a man of action, who had been an intimate friend of Arcesilaüs the Academic at Athens.

[2] These men eagerly adopted his proposals, and he then began conversations with the other exiles. A few of these took part in the enterprise because they were ashamed to disappoint the hope placed in them, but the majority actually tried to stop Aratus, on the ground that his inexperience made him over-bold.

[3]
  While he was planning to seize some post in the territory of Sicyon from which he might sally forth and make war upon the tyrant, there came to Argos a man of Sicyon who had run away from prison. He was a brother of Xenocles, one of the exiles; and when he had been brought to Aratus by Xenocles, he told him that the part of the city’s wall over which he had climbed to safety was almost level with the ground on the inside, where it had been attached to steep and rocky places, and that on the outside it was not at all too high for scaling-ladders.

[4] When Aratus had heard this, he sent with Xenocles two servants of his own, Seuthas and Technon, to make an examination of the wall; for he was resolved, if he could, to hazard the whole enterprise on one secret and swift attempt, rather than in a long war and in open contests to match his private resources against those of a tyrant.

[5] So when Xenocles and his party came back with measurements of the wall which they had taken, and with a report that the place was by nature not impassable nor even difficult (although they declared that it was hard to get to it undetected owing to a certain gardener’s dogs, which were little beasts, but extraordinarily fierce and savage), Aratus at once undertook the business.