Shapeshifter. Coven, #4

Monsters can hide in plain sight. Samantha and Kathy's personal lives have been keeping them busy. Samantha's been planning her wedding, despite the frustrations of Steven's mother and the ensuing tension it creates between the bride and groom. Kathy is struggling with the coursework of her first college classes and spending enough time with Milo, the guy she's been dating. Meanwhile, their new neighbors have invited them to a Halloween party.
But the days leading up to the party reveal oddities and unusual behavior from the people in their lives, culminating in the witches' discovery at the party that a shapeshifter's been lurking among them all week. With no idea who to trust, Samantha and Kathy have only a few hours to find out who the shapeshifter is and how to stop them before they can hurt anyone else-and the party just happens to be full of potential victims. Shapeshifter is the fourth book in the Coven series, which serves as a prequel series to the Under the Moon series.