In 1806, three cousins-Gretchen, Emma, and Penelope-discover their unknown family lineage of witchcraft when a glass bottle containing a powerful binding spell is accidentally broken and their previous hidden powers unexpectedly begin to manifest. Now, beyond the familiar manicured gardens and ballrooms of Regency London, a dangerous, alluring underworld visible only to those with power is now open to the cousins-a world of adventure and secrets that they embrace fully. But unbeknownst to them, by claiming their power, the three cousins have inadvertently opened the gates to the Underworld. Now the dead, ghouls, hellhounds-and the most terrifying of all: the spirits of dark witches known as the Greymalkin Sisters-are hunting and killing young debutante witches for their powers. And, somehow, Antonia is connected to the murders...because she keeps finding the bodies. Can the cousins unravel the clues and mystery behind their heritage and power before another witch is killed...or even worse, before their gifts are stripped away?