For most of his life, Barrett lived at a farm in Concord, Massachusetts, which he lent to the Continental Army as a gunpowder storage before the Battles of Lexington and Concord. He was also Concord's town representative in Boston legislature prior to the American Revolution.
When an unknown person opened fire and sparked the Battle at Lexington, John Parker told the Assassin Connor to deliver a letter to Barrett. At first, Barrett dismissed Connor as a boy looking to play hero, but reluctantly accepted the Assassin's help upon reading the letter.
When the British Regulars reached Concord, Barrett convinced Connor to stay and command his troops, instead of pursuing John Pitcairn. From there, Connor led the men to victory, and was applauded by Barrett for saving countless lives that day.