On September 24, he and Brown, whose company was guarding the road between St. John's and Montreal, met at Longueuil, and, according to Allen's account of the events, came up with a plan in which both he and Brown would lead their forces to attack Montreal. Allen and about 100 men crossed the Saint Lawrence that night, but Brown and his men, who were to cross the river at La Prairie, did not. General Carleton, alerted to Allen's presence, mustered every man he could, and, in the Battle of Longue-Pointe, scattered most of Allen's force, and captured him and about 30 men. His capture ended his participation in the revolution until 1778, as he was imprisoned by the British. General Schuyler, upon learning of Allen's capture, wrote, "I am very apprehensive of disagreeable consequences arising from Mr. Allen's imprudence. I always dreaded his impatience and imprudence."