When Gary Krist read the old woman's diary, he finally knew he had a story.

The Bethesda-based writer, whose new book is "The White Cascade," flew to Seattle in the winter of 2003 to look into a horrific but largely forgotten railroad disaster. Nearly a century before, in late February 1910, a relentless blizzard had stalled two westbound Great Northern Railway trains -- a passenger train and a mail train -- trying to make their way through Stevens Pass in the Cascade Mountains. For days the snow piled up, and the passengers got more and more apprehensive.

"They say it has snowed 13 ft in 11 hours," wrote Sarah Jane Covington, 69, in the diary Krist was examining. "The mts. loom up a thousand feet or thousands . . . the tel. wires are down. No communication with the world."

Krist already knew how the petite, white-haired grandmother's story would end. On March 1, a little before 2 a.m., a wall of snow estimated at 14 feet high and a half-mile wide would sweep the trains off the tracks and hurl them into the ravine below, killing nearly 100 passengers and railroaders, including Covington.

He knew that this catastrophe still ranked as the deadliest American avalanche ever -- an object lesson from an age of technological hubris that would see the Titanic meet its iceberg two years later.

He knew, once he'd seen Covington's diary and a few other documents like it, that he had a wrenching human tale to tell along with the technological one.

What Krist didn't know was whether he could pull it off.

After all, he'd spent his whole career as a fiction writer. He lacked experience with the storytelling constraints imposed by facts.

* * *

At 49, Gary Krist has had the kind of career that should be taught in literary workshops so that wide-eyed young people who want to be writers could learn just what they are getting into.

A tall, bearded man with an easy laugh and a relaxed manner, Krist was such a wide-eyed young person himself once. As a high-school student in Fort Lee, N.J., "I had this romantic notion of being a writer, but I never wrote," he says.

At Princeton, he didn't darken the doors of the creative writing department, though he did start writing (poetry and a few short stories) on the side. It wasn't until he got a fellowship to study in Germany that he buckled down.

He published his first book, a collection of short fiction called "The Garden State," in 1987. It won a prestigious prize and "sold 3,000 copies or something," Krist says, although a paperback edition would boost that number somewhat. Wisely, he decided to hang on to his job as a part-time editor with Kaplan, the test-preparation empire.

In the meantime, he'd gotten married to photo editor Elizabeth Cheng. Eventually, Cheng's work would draw the couple to Washington, where she works at National Geographic.

Lesson No. 1: A spouse with a regular paycheck helps.

Krist's next step was to write a novel that "more or less everyone agreed was not something I should publish." He salvaged portions of it in "Bone by Bone," another story collection, which sold even less than his first.

Time to get practical.

"I wanted to quit my day job," Krist says with a laugh, "and I knew that writing literary short stories was not going to allow me to do it."

"Bad Chemistry," a thriller set in the Maryland suburbs, was the result. As its author had hoped, reviewers saw that it contained more psychological insight than most of its ilk. David Willis McCullough wrote in the New York Times that Krist's book "walks and quacks" like others in its genre but ends up as "something more devious than the duck it pretends to be."

It sold a lot more than Krist's stories had, although not enough to make bestseller lists. More important, it got Random House excited about publishing another thriller featuring ex-cop Kate Baker. The idea was to build a brand. "You know, people read the third Kate Baker book and then they'll go back and read the first Kate Baker book," Krist says. He signed a contract in the low six figures, far more than he'd made on a book before.

Then he discovered he couldn't write the damn thing.

"I just said, 'I'm through with that character,' " he recalls. He figured using the same protagonist over and over would transform an idea that initially had merit into "total hack work." He mentions zillion-seller Patricia Cornwell's medical examiner heroine, Kay Scarpetta, as a case in point.

Lesson No. 2 : Maintaining your artistic integrity is a good and noble thing to do. Especially if you don't think too hard about the opportunity cost.

"Chaos Theory," the novel Krist wrote instead, featured two D.C. teens, a petty drug deal gone bad and a criminal nightmare beyond their sheltered imaginings. Like its predecessor, as The Washington Post's Jonathan Yardley noted, "it can be read as a thriller," but "it is also about larger subjects." Among those Yardley mentions are "the complex interaction between the city of Washington and the suburbs" and "the disarray that descended upon the city during the catastrophic mayoral regime of Marion Barry."

Sequel or no sequel, it seemed as though Krist had a nice little literary thriller thing going. So naturally he broke the mold.

His next book, "Extravagance," was a high-concept, partly historical novel about irrational economic exuberance, set simultaneously in the wildly optimistic London of the 1690s and the wildly optimistic New York of the 1990s. Krist used a single set of characters to tell a single story in which the action cuts back and forth between these parallel economic universes.

"I wrote my two thrillers, they bought me a little time," he says. "So let me invent my own genre."

It's one he seemed suited for. Krist has "a rare combination of a literary sensibility and logical rigor," says science writer Robert Wright, an old friend. Wright thinks the economic insights in "Extravagance" could have been turned into a "sheerly analytical" piece of social science that "would have gotten attention." As fiction, it got its share of attention too, much of it positive.

"Krist's ambition is laudable, and the novel is a worthwhile read," says Publishers Weekly, "especially when he gets his complex narrative to click on all cylinders."

But the attention that counts most for American authors comes from the New York Times, whose reviewer was less enthusiastic. He also devoted considerable space to picking factual nits -- not always correctly, Krist maintained in a too-little, too-late letter to the editor.

Lesson No. 3: "Imagine that the whole world gets to read your job evaluation."

Small wonder that Krist was a bit down when he met his agent, Eric Simonoff, for a lunch that would change his writing life.

"Have you ever thought about nonfiction?" Simonoff asked.

* * *

Yes, he had -- and not just because of one bad review.

"I was tired of having everything come out of my own head," Krist says. Plus, he'd loved talking to historians while researching "Extravagance": "It was just like fresh air for somebody who'd been sitting in his basement for too long."

And yet, he'd always thought of himself as a fiction writer. At this stage, he wondered, would he even be allowed to make the switch?

Simonoff reassured him and sent him off to find a story.

Serendipity and Google led Krist to that 1910 avalanche, known as the Wellington Disaster after the tiny mountain community where the Great Northern trains were destroyed. He was Googling the Duke of Wellington -- he has long been fascinated by English history -- when up popped a reference to a Wellington he'd never heard of.

He clicked on a Web site run by retired Boeing executive Bob Kelly, who'd been researching the avalanche since 1990. Determining that there were no major books on the disaster, Krist gave Kelly a call.

Kelly was skeptical. Over the years, he says, he's been contacted by numerous writers and producers. Nothing had ever come of it. "Gary was just the next one," he figured -- until the novelist showed up on his doorstep with "kind of a gleam in his eye."

Kelly's collection of Wellingtoniana was a godsend to Krist. In it, he found Covington's diary, along with a letter discovered near the body of another passenger. Ned Topping had been writing his mother, making new entries day by day as the snow kept falling and the trains kept failing to move. The night before the avalanche, he and many other passengers had resolved to try to walk to safety.

"I expect to leave in the morning," he wrote. "Oh, if I ever get out of this place, how happy I will be."

What Krist didn't find in Kelly's trove was anything personal relating to the man he knew would be his story's central figure.

As the superintendent of the Great Northern's Cascade Division, James O'Neill was responsible for the decision -- reasonable at the time, fatal in hindsight -- to leave the passengers at Wellington while he and his crews worked tirelessly but futilely to clear the tracks. Kelly had been trying for years to track down an O'Neill descendant. Krist hired a genealogist who came up with one.

"I remember calling up Bob and saying: 'I found the granddaughter! And she has two boxes of stuff!' " Krist recalls.

In the end, Krist says, he used every scrap of personal information he could obtain about those involved in the disaster. Did he ever wish he could put words in silent passengers' mouths? Make the ones who did leave written records more articulate than they really were?

Of course.

But he knew he couldn't.

"Since I have this history as a fiction writer, I knew I had to be especially scrupulous," he says. "Nonfiction writers these days really stretch it. I don't like that."

Krist says he got the same craftsman's pleasure out of constructing the narrative, "balancing the pace and background," that he does with fiction. He's working up another nonfiction proposal now. "I loved the whole process of writing this book," he says. "I want to duplicate this experience at least a couple of times more."

That said, he's also got a novel underway ("I'm trying to work on it on Fridays"), and there are a number of stories in his files, in various stages of completion, that he confesses to looking at now and then.

The newly minted nonfiction writer laughs.

"I still think that maybe what I'm best at is short stories," he says.