It's 1983 and eleven-year-old Cat Rossi watches the launch ramp at her dad's marina in Arizona. She's used to the carousel of single summer friends who visit until she meets Will Henderson, the only son of a wealthy doctor. They bond over ice cream, boat rides, and pinky promises, and when August ends, Will vows to come back next year.

Over the next decade, Cat spends the off-season waiting for Will to return for the summer, and every year their connection is tested as they wade the awkward waters of adolescence into adulthood in the 80s and 90s. Torn between family obligation and her desire to forge her own path, Cat must decide how much she's willing to risk for the greatest love of her life.