Rosa Pelham lives in a castle in Berkeley Springs, West Virginia, built by her late husband to woo her during their courtship, a story rooted in local legend. Still in her early thirties, her lavish lifestyle has pushed her to the brink of bankruptcy. One night on the rooftop, her current lover plunges to his death, leaving behind a note that points her toward a nearby spring whose waters grant extraordinary longevity.
One hundred fifty years later, Rosa and her son Wyeth still reside in Berkeley Springs, living above his struggling thrift store. Both are jaded and quietly burdened by their unnatural longevity. After decades of estrangement, Wyeth's father, Albert, returns with a warning that the spring sustaining them may be at risk of contamination from nearby oil and gas drilling.
Just down the road lies the estate of the Scowl family, owners of one of the country's largest fossil fuel companies. Berm Scowl, the current CEO, and his sister Pawpaw are summoned for an emergency meeting with their ancestor Richie Scowl. Richie's stolen supply of the spring's water is running dry, and he is determined to find its source.
Rosa, Albert, and Wyeth make a midnight journey to the cavernous springs, only to be followed by Pawpaw, whose presence complicates an already dangerous situation.
Hovering above it all is George Washington, who once frequented Berkeley Springs and now narrates events from beyond the grave. From his vantage point, he observes the town and communes with the living through the Roman Baths, where past and present blur.
As tensions rise, Rosa seeks out Mosella, a local fortune teller who warns that Wyeth is in danger. His unrest traces back to the long-ago death of his best friend, Chase Sterling, a tragedy he believes he caused and one that continues to shape his life.
The castle now belongs to Peter Brimewall, an aging white supremacist obsessed with the young Rosa who once lived there. Richie attempts to gain access to the land under the guise of drilling, but Brimewall refuses to cooperate.
Fragments of the past resurface, including Pawpaw's violent break with Richie as a teenager and the betrayals that drove her away. As Richie closes in on the springs, old alliances reform and new ones emerge. When he finally locates the source, he is met by Wyeth, Pawpaw, and others, and a brutal confrontation leaves him gravely injured.
In the aftermath, as lives hang in the balance and long-buried truths come to light, Rosa and Wyeth are forced to reckon with the cost of their extended lives. Love, guilt, and survival converge at the edge of the spring that has defined them.