Benedict Arnold
In July 1780, he asked for, and got, command of West Point.  Secretly, he planned to surrender it to the British. But Arnold's contact in the British army, Major John André, was captured.  André had been carrying papers Arnold had given him that revealed the plot. Upon learning of André's capture, Arnold ran away down the Hudson River to the British ship HMS Vulture. Arnold was almost captured by the forces of George Washington, but he did get away.