Louise Brenner's childhood summers at Blanche Lake, Minnesota, are filled with magical adventures alongside the Kool Goons, a close-knit group of lake kids. Bound by their love for each other, they embark on thrilling canoe trips into the mysterious inlet, where unimaginable events unfold. Immersed in the rich folklore of Selkies-mythical beings who can transform from seals into humans-and the haunting Inuit tale of Sedna, Louise embraces the enchanting narratives that shape her time at the lake.

Drawn to the water, Louise spends countless hours envisioning herself as a nymph, a sea creature-a part of the captivating myths she holds dear. Her dearest friend, Ruby, becomes an inseparable companion at Blanche, until her sudden disappearance at the age of sixteen. Ruby's departure, and the manner in which she vanishes, leave a lasting impact on Louise, burdening her with a secret she cannot divulge.

Years later, a former lake kid reaches out to Louise, proposing a Kool Goons reunion at Madsen's Resort on Blanche. Initially hesitant to confront her haunting past, Louise realizes that returning to the lake might be her only opportunity to liberate herself from a past that has unfairly ensnared her.