We see them together in the book’s opening pages, as they leave their father’s Montana ranch for the Western Front of World War I. Distinct as brothers in a fairy tale, the boys are partly characterized by their father’s look around their now-empty rooms: Alfred, the striver and future politician, has left behind “sentimental bric-a-brac, dumbbells, self-help books”; Samuel, the gentle and aspiring naturalist, will be separated from stuffed animals and microscopes; the storage trunk of the untamable Tristan contains “cartridges for a Sharps buffalo rifle, a rusty handgun of unknown origin, a jar of flint arrowheads, and a bear claw necklace” that he probably got from the Cheyenne named One Stab, “whom Ludlow often felt was more the boy’s father than he himself.”

We learn that the elder Ludlow has “mismanaged” the “secondary life lived through his sons,” but it is the brotherly bond, more than any paternal one, that dominates the book, uniting and strangling the three young men. After Samuel is cut down in France by gunfire and mustard gas, Tristan cuts out his little brother’s heart (for burial under the Big Sky of home) and then, deranged with grief, scalps several German soldiers, taking care to observe a bit of technique that Harrison passes on to the reader: “You couldn’t scalp a beheaded man because you needed an anchor to gain a good fulcrum.” Tristan’s later wanderings and outlawry are awash in violence, and the novella sometimes feels ready to crumble beneath all its gunplay and carnage and staginess.

And yet Harrison never lets go of several different literary schemas — Celtic, biblical and classical — that seem to frame and discipline the story. The Tristan of legend steals his uncle’s intended bride for himself; Harrison’s Tristan similarly provokes his brother’s jealousy by making off with Susannah, the girl Alfred was supposed to marry, although Tristan really desires her only in order to create a replacement child for the dead Samuel. As in the Old Testament, Susannah is spied upon when she’s at her bath, and just as allusively, when One Stab picks up the ill-­fated Samuel’s saddle, it is “as if he were picking up doom herself, doom always owning the furthest, darkest reaches of the feminine gender. Pandora, Medusa, the Bacchantes, the Furies. . . .”

The story’s narrative voice is arbitrary and godlike, always very distant but by turns lyrical and essayistic, superbly telling instead of showing: “Susannah’s character owed more to the early 19th than the early 20th century.” When the narrator has the future on his mind, he doesn’t foreshadow what he can simply foretell: We learn that Tristan will die “on a snowy hillside in Alberta late in December in 1977 at the age of 84,” nearly 50 pages and more than 50 years before it happens.

Not so much world-weary as cosmically tired, Harrison’s storytelling is sometimes hushed and sometime sonorous, rolling out on waves of complicated syntax that are averse to commas. This tale of brothers has so much on its mind that the author’s choice of the compact novella form seems almost perverse, a kind of stunt. A Tolstoyan view of the world (“There is little to tell of happiness — happiness is only itself, placid, emotionally dormant”) must also make room for “the Cheyenne sense of fatality that what had happened had already happened.” By the time “Legends of the Fall” is finished, it has the reader believing that life is little more than death’s back story.