For years, rumors have swirled about an exclusive, women-only social club where the elite tastemakers of New York City meet. People in the know whisper all sorts of claims: Membership dues cost $1,000 a month. Last time Rihanna was in town, she stopped by and got her aura read. The women even handpicked the city's first female mayor. But no one knows for sure. That is, until journalist Jillian Beckley decides she's going to break into the club. But the deeper she gets into this new world, the more she learns that bad things happen to those who dare to question the club's motives or giggle at its outlandish rituals. The select group of women who populate the club may be far more powerful than she ever imagined. And far more dangerous too.

After her former band shot to superstardom without her, Claire reluctantly agrees to a gig as a playgroup musician for wealthy infants on New York's Park Avenue. She is surprised to discover that she is smitten with her new employers, a welcoming clique of wellness addicts. There is perfect hostess Whitney, who is on the brink of social-media stardom and just needs to find a way to keep her flawless life from falling apart; caustically funny, recent stay-at-home mom Amara, who is struggling to embrace her new identity; and old money, veteran mom Gwen, who never misses an opportunity to dole out parenting advice. But as Claire grows closer to the stylish women who pay her bills, she uncovers secrets and betrayals that no amount of activated charcoal can fix.