In one golden summer, Frances trades her working-class world for an elite Maine lakeside estate—where privilege and betrayal turn into a deadly game.

Frances believes she’s found a ticket to paradise when a wealthy couple hires her for the summer as their mother’s helper at their lakefront summer home in Maine. The vintage wooden boats, the days at the country club, a shiny new bicycle, and a tennis racquet—suddenly Frances has everything her modest childhood lacked. Best of all, she gets to spend the summer with Forrest Emerson, her father's charismatic childhood friend who escaped their neighborhood when he married into money.

But below the glittering surface of Lake Catherine, nothing is what it seems. When Forrest’s wife, Regina, pulls Frances into her private obsession, the girl finds herself witness to the intimate secrets of adult lives. As the summer heat builds, so do the tensions within Wonderland’s walls. By Labor Day, a death will shatter the seemingly perfect family, leaving Frances to question everything she thought she knew about privilege, power, and the price of belonging.