It is just possible, when you realize that the author of the “epic Civil War romance” Amelia is the guy who’s going to play all of the characters—male and female, black and white, Yankee and Rebel—who aren’t the prickly Pennsylvania spinster of the title, that you will say quietly to yourself, “Oh dear.” Many a project, after all, has come to grief on the shoals of vanity.

But give it time. After a slow start, Amelia turns out to be a gratifyingly solid bit of storytelling—an implausible but still involving hero’s quest of near-classical proportions.

The précis: Amelia (Shirleyann Kaladjian) has settled into a life of hard but gratifying work running the dairy on her family’s Pennsylvania farm, untroubled by thoughts of marrying any of the stick-in-the-mud locals, when a new clerk shows up at the local general store and proves himself the kind of guy who likes a smart, stubborn woman like her. One mildly overlong fractious-romance sequence later, the two are on the cusp of love—but the Union, in April of 1861, is on the cusp of war, and Ethan (Alex Webb) is the kind of guy who signs up to serve.

He declares himself; she stammers, tongue-tied, and before she can recover, he’s off to battle, leaving behind a wife who’s never quite said she loves him. When days and weeks turn into months and years, Amelia sets off to right that wrong. She hitches up her family’s sturdy bay mare, riding off to his regiment’s last known destination, a place called Gettysburg. Ethan, it hardly needs saying, will not be there.

What follows is a grueling odyssey, astutely rendered: Amelia tracks her husband doggedly south, shedding first pounds of weight, then (after her luck flags and a rebel soldier steals her horse) her very identity. And still she drives on, now in disguise and in the Union ranks, hurling herself into battle and in the direction of Ethan, who may be among those taken to a place whose name still reeks to history: the Andersonville prison camp, where thousands of Union prisoners perished in crowded filth.

By now, it will be apparent that Amelia will turn out to be a dark love story, and one that seems a whit over-reliant on coincidence, but there’s something about the passion Webb brings to the storytelling—and the craft and commitment he and Kaladjian bring to their performances—that makes it gripping. The play’s procession from county social to Confederate prison feels somehow inevitable, its unavoidable tragedy fully earned. After 90 minutes in a room with just two bodies on a stage, you leave with a head full of vivid pictures, indelible images of woman consumed by her purpose, and a nation consuming itself.