Benedict Arnold develops a plan to capture Fort Ticonderoga in New York in order to get cannon for Boston. Before leaving for Massachusetts, he tells several men in his home colony of Connecticut about his plan. These Connecticut men organize a force with Ethan Allen and the Green Mountain Boys, who live only a few miles from the fort.
Arnold, unaware of this plan, gets approval from the Massachusetts army to raise a force in Western Massachusetts to attack the fort. Upon learning that Allen is assembling an attack, Arnold, by himself, rushes to meet Allen's forces and demands to lead them. They refuse, but allow him to come along.
The British do not have the fort guarded well, and do not have a large garrison. The Green Mountain Boys easily enter the fort at dawn and capture the garrison without any deaths. Allen and Arnold then fight over command and who deserves credit for the victory.