Trinity Matiri is a young woman from New York City preparing to attend college in Texas with a piano scholarship. During her summer vacation, she accompanies her mother to England for her grandfather's funeral service and discovers unsettling secrets. Dad was murdered by members of a secret society when she was a child, and she belongs to a family of spies and witches. Mom is an assassin for MI6, and Grandpa was an intelligence officer. As for Grandma, she's a retired nurse and a witch who tells Trinity she will inherit her talents, and she's about to engage in a time-traveling adventure.

Trinity's mission is to protect the timeline from extremists sent to the past by that secret society. First, she must track them to World War II, where they are assisting the Nazis' invasion of North Africa. Second, she must prevent them from destroying her family during the Jacobite revolt in the mid-eighteenth century. To succeed, she must seek her ancestors, embrace her entire heritage, and combine it with her musical talents.

Finding herself alone in London at the end of the Blitz in 1941, Trinity joins the British Army and becomes an intelligence officer. Her first assignment is in Cairo, a city infested with enemy spies.