Age of Empires III's campaign follows three generations of the fictional Black family, narrated throughout by Amelia Black.
Act I — Blood: In the late 16th century, Morgan Black serves as a mid-level commander with the Knights of Saint John. He's defending Malta from an Ottoman assault led by Sahin "the Falcon" when his superior, Alain Magnan, discovers a hidden stone library describing the Lake of the Moon—believed to be the Fountain of Youth—and a secret society called the Circle of Ossus that wants to reach it first. Morgan is sent to the New World to find the Lake before they do.
The journey takes him through the Caribbean—where he clashes with the pirate Elisabet "Lizzie" Ramsey—to the jungles of Yucatan, then to Cuba, and finally to Florida. Along the way he gains Lizzie's respect, fights alongside Aztec allies against Spanish conquistador Francisco Juan Delgado de Leon, and captures the Ottoman commander Sahin. In Florida, Sahin reveals the truth: he was trying to prevent the Circle from claiming the Fountain, not take it for himself. Alain, Morgan's own superior, leads the Circle of Ossus. With Lizzie's fleet and a seized fortress cannon called a Fixed Gun, Morgan's forces destroy the Fountain and kill Alain. Morgan returns home with one unresolved question—whether the water in his canteen was ever truly what the legends claimed.