Knightwatch, the most elite knight school in 19th-century England, where Archie's older brother, Alexander, and their friend Calico are training to become Black Knights. Then, a secret file is stolen and Alexander is framed for it—Archie sets out to find the real thief, but instead, he stumbles upon an even bigger mystery. Friendships are tested, promises are broken—and when their very lives are threatened, Archie realises he must race against time to uncover the truth about a Black Knight who was killed seven years ago: Calico's father.