In an emotionally charged trial John Adams defends the British sentries involved in the Boston Massacre who contend they were provoked into firing on the assembled crowd. John's success brings him offers of positions in the Massachusetts government. But after John Hancock rouses a crowd to tar and feather a representative of the British East India Tea Company and the British respond to the growing unrest with oppressive measures, John instead speaks against the British policies and chooses to represent Massachusetts in the Continental Congress.

After viewing the dead and wounded on the battlefield of Concord, John Adams takes up the cause of Independence. Frustrated by the caution of delegates from colonies that do not share Massachusetts plight, the inexperienced politician is abrasive, obnoxious and even insulting. But with the advice of Abigail and Ben Franklin he soon learns he has allies, to cultivate them, to bide his time and to seize opportunities. Following John's nomination, George Washington takes charge of the army and enjoys successes despite supply shortages. Back at home, Abigail and the children risk supporting the war effort in most tangible ways but find Mother Nature more threatening.

Over the emotional objections of Abigail, John Adam and his son endure turbulent seas and an encounter with the British Navy to join Ben Franklin on a diplomatic mission to Paris. But Ben cannot restrain John's abrasive personality which is even less well suited to Paris than Philadelphia.

Following the surrender of the British, John secures a long sought loan from the Dutch and returns to Paris to oversee the peace treaty. John can no longer bear his absence from Abigail and invites her to Paris which immediately overwhelms her with it's opulence. John is appointed ambassador to England but soon longs to return home to participate in the formation of the new government and, like Abigail, to be reunited with the children. They return home to an overwhelming welcome and John reluctantly returns to public service.

Following the peace treaty with England President Adams struggles to avoid war with France despite pressure from his Federalist cabinet and French provocation. John finds the price of peace to his career and the price of his long career of public service to his family is indeed high.

In retirement John Adams laments the perils of a long life; loss of loved ones and growing irrelevance. But out of tragedy John rekindles his broken friendship with Thomas Jefferson and lives to discuss John Quincy's ambitious presidential agenda with him.