It is remarkable that award-winning Maine author Jean M. Flahive tells such a big story in such an economy of space. “Railroad to the Moon” completes the story begun in the prequel, “Billy Boy,” a novel based on a true story of a young, mentally challenged boy from Berwick, Maine, who volunteered to fight in the Civil War. “Railroad,” subtitled “Elijah’s Story,” picks up at the close of the war and weaves in the true story of Oren Cheney, the Freewill Baptist minister and the founder of Bates College. Runaway slave Elijah is in Maine by the grace of Billy’s hand and the Underground Railroad. His story intersects Cheney’s over the burden Elijah carries for those he left behind.

It’s important to have some understanding of “Billy Boy” to appreciate its sequel. Once engaged in warfare, Billy Laird was separated from his friends in the 17th Maine. Bewildered and overwhelmed by the war, he deserted. He encountered Elijah, who was weakened by constant running to avoid slave catchers, and nursed him to health and then helped guide him north to freedom. Billy ultimately ended up being tried as a deserter and was shot at Fort Preble on Casco Bay, despite President Lincoln’s pardon. Word of the pardon arrived too late.

“Railroad to the Moon” is the story of Elijah living with Billy’s parents on their farm, and most importantly, the story of his special relationship with Jamie, Billy’s grief-stricken younger brother. He first finds Jamie so devastated by Billy’s death that the boy is mute. Elijah proves the only one capable of bringing him out of his shell. Though torn over missing those he left behind, Elijah feels honor-bound by a pledge he made to Billy to be Jamie’s surrogate older brother.

Well into the book, Elijah explains his relationship with Jamie to Talitha, the girl he loves and who loves him, when he briefly returns south after the war. “Jamie, suh, he a good boy. He like a bird with a broken wing when Billy, suh died… If Elijah don’t go back, other wing go and break, and Jamie, suh, he ain’t never go and fly again.”

Talitha is incredulous when Elijah tells her he must leave to return to Maine. To which Talitha replies angrily: “He a white boy? You think white folk do you the same?”

“Some do. Talitha. Some do.”

It greatly pains Elijah to leave his father and Talitha a second time to return again to the North. He draws strength from something a woodsman told him in the depth of his first winter in the North, about life beneath a frozen lake. “Even though you can’t see it, life teems beneath the frozen lake, waiting for spring.” Elijah wonders if seeing Pappy and Talitha, “the girl he had once kissed in a cornfield,” if having them back in his life is the spring buried beneath the frozen lake of the pledge he feels he must honor.

The story of the endeavors of Oren Cheney to raise funds to start a school in the South for newly freed slaves, and also to bring them to fledgling Bates College in Lewiston, is where Elijah’s and Oren’s stories converge. In the unfolding, there are dangerous encounters with slave catchers while Elijah is again in the South, and a deadly scene with “Buckra,” the overseer who brutalized Elijah, causing him to run off in the first place. And there is also the valiant effort to bring home the body of a Berwick boy who’d died at the battle of Fredericksburg and was buried in a Virginia field.

“Railroad to the Moon” is a big story about one of the greatest injustices in American history, about the desire for freedom and belonging, and about honoring one’s word despite grave personal costs. It’s also a story about a very special friendship — as well as a deeply fetching love story that necessitates overcoming one’s prejudices and fears to trust a people who have oppressed you.

Reading “Railroad to the Moon” made me think about classic stories of the agony of youthful attachment and loss, stories like John Steinbeck’s “The Red Pony,” and Marjorie Kinnan Rawlings’ “The Yearling.” This is a book for readers of all ages who love a good story. The characters are fascinating and richly drawn and the pathos at the end is heart-rending. The story is simply a gem.

Frank O Smith is a writer, ghostwriter, and writing coaching whose novel, “Dream Singer,” was a finalist for the Bellwether Prize. He can be reached via www.thewritinggroup.com.