Nick is on a mission. Deeply troubled by the loss of a young friend at the Battle of San Jacinto, he wants desperately to return to the scene of the battleto alter history. But when he furtively opens the mysterious trunk, now in Mr. Barrington's attic, he is transported instead to Gonzales, Texas, in 1835. There he meets many historical characters, including the young Alamo defenders William King, John Gaston, and Galba Fuqua. (Will, Johnny, and Galba are introduced in Book 1 of the series.) Once befriended by them, Nick finds himself caught up in the excitement leading up to the Battle of Gonzales.

Hannah and Jackie, knowing they must stop Nick and bring him back safely, follow by trunk in hot pursuit. After falling down a riverbank, Hannah is rescued by Lieutenant Ramirez, a member of the Alamo de Parras Company of dragoons sent to retrieve the Gonzales "Come and Take It" cannon. The girls are escorted to his camp, where they learn about life in the Mexican army and the tensions that are building in Texas.