Princess Elizabeth's Spy by Susan Elia Macneal (Maggie Hope series Book 2)

This is the second installment of the Maggie Hope series by Susan Elia Macneal

Summary
-Maggie is back. This time she's completed her MI-5 spy training and is itching to put those skills to use. Much to her great disappointment, she will not be heading out on reconnaissance missions to collect intelligence for the British war effort. Instead, she's going undercover at Windsor Castle, to tutor the young Princess Elizabeth in math. The upstairs-downstairs Downton Abbey-style world of Windsor Castle proves much more dangerous than she thought as a murder is committed. This throws the whole royal family into disarray and she much race against the clock to protect both the royal family and England against a threat much larger than everything