Rory Wilson and Celeste Markham are friends. Or that’s what everyone thinks. Their boyfriends are co-captains of the soccer team, they hang out with the same group, and they’re even going to the same college in the fall. The truth is, they've been secretly sabotaging one other since middle school, and the only thing keeping their frenemy-ship from total destruction is that they each know the others’ darkest secret. 

When Rory spies her boyfriend hooking up with Celeste, the endgame begins. Now she has plans to finally get Celeste exiled from the friend group so she no longer has to play second-best to the insufferably perfect Celeste. It'll happen at the beach house where the entire group is kicking off the summer with a week of chilling by the pool, partying, and—if Rory plays her cards right—shocking revelations that will turn everyone against Celeste. She has a plan, and it's going to work. No matter what it costs her.

But taking down a frenemy is no easy task, and Rory’s not the only one in the house bent on destruction. Either Celeste is even more devious than Rory realized, or someone else is stealthily playing the circle of friends against one another. As a storm strands them all in the house, tensions rise and the dangers escalate. Rory doesn't know whether she's the target of this secret revenge, or if Celeste is. Will she be the one to end up dead? Or the one left without an alibi?