Vacationing in Britain, Mercedes is stalked by someone who will kill to learn what she knows about hidden gold and the secrets of Shakespeare's blood.
Mercedes Maxwell finds a handwritten notebook while touring Britain. The writer claims that William Shakespeare had a brother named John who was an agent for James I of Endland. Captured by outlaws, John died rather than reveal the location of a trove of Spanish gold. When it becomes obvious that someone is willing to kill for the notebook, Mercedes decides that the story might be true.
The killer embarks on a reign of terror. Those who know about the journal are murdered and left posed as characters from Shakespearean tragedy. When he turns his attention to Mercedes, she realizes that solving the clues from the journal is the only way to stop him. Although she can call on several people for help: a police sergeant, an actor, and a misanthropic historian, she wonders if anyone can be trusted where treasure is concerned.
The unraveling of the clues becomes critical as the killer tracks Mercedes’ movements. The message from the man who called himself John Shakespeare leads her across Britain in a fight to find the treasure, stay alive, and learn the secrets of Shakespeare’s blood.