When Silas Heap unseals a forgotten room in the palace, he releases the ghost of a queen who lived 500 years earlier. Queen Etheldredda is as awful in death as she was in life, and she's still up to no good. Her diabolical plan to give herself everlasting life requires Jenna's compliance, Septimus' disappearance, and the talents of her son, Marcellus Pye, a famous alchemist and physician.