The Traitor's Blade

In the fifth installment of the Blackthorn Key series, Christopher, Tom, and Sally return to London amid relief from the plague and a royal reward, only to find themselves entangled in a dangerous conspiracy. An ambush leaves an old friend gravely injured, and a cryptic warning suggests a plot to assassinate the king. As they delve into the mysterious clues, they uncover a sinister scheme that threatens the entire realm.