In the sweltering heat of one summer in Grinnell, Iowa, Claire and Don Lowry discover that married life can fall apart seemingly overnight. Don, the town's most successful real-estate agent, is hiding the fact that their home is in foreclosure from his wife, Claire. She has secrets of her own: she's bored, lonely and lusts after Charlie Gulliver, a failed actor who has returned home to sort out his father's affairs.

As the summer lingers and the temperature rises, the town's adults grow wilder and more reckless while their children grow increasingly confused. Claire, Don, and their neighbours and friends find themselves on an existential odyssey, exploring the most puzzling quandaries of marriage and maturity. When does a fantasy become infidelity? When does happy routine become boring monotony? Can Claire and Don survive everything that befalls them in this one summer, forgive their mistakes, and begin again?

Summerlong is a deft and hilarious exploration of the simmering tensions beneath the surface of a contented marriage that explode in the bedrooms and backyards of a small town over the course of a long, hot summer.