A multigenerational mystery set in the Pacific Northwest. Months after spying a bottle wedged into a fallen cottonwood snag in the Columbia River, Ernest pulls it from the river. The bottle's note connects Ernest, an old man living in a tiny Oregon town, to teenage Annie, and provokes a mysterious and sudden friendship between Ernest's daughter Amelia with Sarah, the daughter of the most recent resident of the home Annie once occupied. The two middle-aged women are keen to learn more about Annie and her secret, and in the process, they're forced to confront unfinished business with their mothers, intimate relationships, and regrets over life choices.