Royal Blood

Penniless and thirty-fourth in line to the throne, Lady Georgiana Rannoch finds herself in a truly draining state of affairs. To escape her hateful brother, Georgie accepts an invitation from the Queen to represent the royals at a wedding in Transylvania. But at the macabre- looking castle, Georgie finds the bride with blood running down her chin, and a wedding guest is poisoned. Now it's up to Georgie to save the nuptial festivities before the couple's vows become: to love and to cherish, till undeath do them part...

This is #4 in A Royal Spyness Mystery.