When a Sikh soldier saves Jack Cameron and alerts him to the existence of a conspirator working with the Sudanese slavers the English are trying to vanquish in late Victorian North Africa, Jack gives the man a deathbed promise to avenge him by discovering the betrayer. Gravely wounded soon after, Jack winds up on his uncle's Sussex estate to heal, and as he convalesces, he discovers that artist Theodore Phyfe is using the terrace beneath his window to paint. Ted is often accompanied by his sister, widow Addie Hoodless, and the two siblings are unaware that they have a silent witness to their conversations. Jack becomes fascinated by Addie, but when he learns that her brother has been commissioned to paint portraits of the Black Dragoons' senior officers, he insinuates himself into Ted and Addie's life to gain access to the artist's studio, hoping to discover something from his proximity to the officers, since he believes one of them to be the traitor.
