Even though Chris Bohjalian's "The Jackal's Mistress" is not shampoo, the plot does have the kind of rhythm conjured by the three words found on pretty much all bottles of the stuff: lather, rinse, repeat. Also like those words, his latest is pleasing in its directness but simultaneously lacks a certain depth.

That doesn't mean the novel is a drag to read. It's hard not to get pulled in from the first sentence: "She took the carving knife from the pumpkin pine table and pointed it at the stranger, the handle hard in her hand." The "she" is Libby Steadman, a woman whose husband has gone off to fight for the Confederacy, leaving her, a 12-year-old niece and a freed Black couple to run the gristmill on their Virginia property.

The intruder, a former Confederate soldier who is part of a band of marauders known as Mosby's Rangers, is up to no good. Libby will somehow have to dispatch him. Little does she know he's just the first in a long line of such confrontations she'll have to deal with as the Civil War rages in its penultimate year and she becomes the caregiver of a Union officer who was left to die in a nearby house.

Interestingly, the bare bones of the story are based on real events. In September 1864, Bettie Van Metre, the wife of a Confederate soldier, rescued Lt. Henry Bedell of Westfield, Vt., who was wounded by rebel shelling near Opequon Creek in Berryville, Va. She hid him and nursed him.

Through Libby, Bohjalian tries to work out the motivation for someone such as Van Metre saving an enemy. His success is predicated on whether you buy what he's selling.

I had a hard time believing someone would jeopardize a whole household, and yet I know that a flesh-and-blood woman did that very thing. The best the "Flight Attendant" writer can come up with for explanation is that Libby "needed — and needed was the right verb, it was a compulsion — to save the life of a Yankee stranger."

The Jackal

This "need" leads Libby to embark on a ludicrously dangerous mission that also strains belief, but also actually happened in real life, proving once again that truth is stranger than fiction. Along the way, she meets up with several bad actors, and even more of them after she returns. A war is on, but still. The repetitiveness of these confrontations is wearying.

An anachronistic feel also plays havoc. Bohjalian evokes the era with word choices like "gallinippers" (mosquitoes) and sentence structures like "As he worked, he was saying something about a doctor, but the words were but a stream." Inconsistency of language is the problem, though, as is a general hastiness around propriety. Libby doesn't think soldiers would dare search a lady's bedroom but a lady can drink whiskey on a porch with a Yankee? Oh, but Libby Steadman is "headstrong," so I guess that makes it all right?

Despite all that, "The Jackal's Mistress" gallops along, sweeping us up in its heart-pounding final pages, almost lifting free of its trappings. Actually, it would have been a better novel if it had done so.

The Jackal's Mistress

By: Chris Bohjalian.

Publisher: Doubleday, 336 pages, $29.