On September 21, 1780, Benedict Arnold met Major John Andre, the British adjutant general, in a wood near Stony Point on the Hudson, and handed over papers describing the defences at West Point, the fortifications he commanded and had agreed to give up. The meeting was supposed to be on a ship. The sloop Vulture had been driven off by American guns, and Andre was on the wrong side of the lines and behind his own schedule.
Arnold was the best commander. He had taken Ticonderoga in 1775, led the expedition to Quebec through the Maine wilderness, won at Valcour Island on Lake Champlain, and been the man who turned the first battle of Saratoga around with a charge he had no orders to make. He had also been passed over for promotion by Congress, court-martialled for his conduct at Philadelphia, and married to Peggy Shippen, whose family was loyalist and who was in contact with the British in New York.
The deal was 20,000 pounds. Arnold had been negotiating since May through an intermediary, and he had asked for West Point specifically, and had got it in August by asking Washington for the command. He then set about making it indefensible: moving guns, letting the garrison shrink, and leaving the great chain across the Hudson in need of repair.
What caught him was that Andre did not get back. He was stopped on September 23 on the road to New York, by three militia men who searched him, found papers in his boot, and took him to North Castle. Washington was informed and rode to West Point that morning. Arnold, who had been told of Andre's capture while at breakfast, got to the river, took a boat to the Vulture, and was gone.
Andre was hanged as a spy at Tappan on October 2, after a board of officers including Lafayette and von Steuben found he had been behind American lines in disguise. Washington had offered to exchange him for Arnold and the British would not do it. Arnold was commissioned a brigadier general in the British army, served in Virginia, and died in London in 1801. His name means treason.