Secrets and Spies: Inferno by Jo Macauley (author)

Fifteen-year-old Beth Johnson is a talented and beautiful young actress. She is also a spy. Basking in the long hot summer of 1666, Beth is looking forward to her first leading role on the stage. But when she receives an anonymous letter, the world turns upside down for Beth and her friend John. Henry Vale, the dangerous mastermind behind a clever plot to kill the King, has kidnapped John’s sister. Now he is blackmailing John to lure the king into a deadly trap. Will Beth be able to rescue John’s sister before the whole of London goes up in smoke?