Anything for a Pal : THE LION AT THE DOOR <i> by Newton Thornburg (William Morrow: $18.95; 288 pp.; 0-688-08820-1) </i>

In Newton Thornburg’s latest suspense novel, big, strong, decent Tom Kohl sits in a Seattle bar with his cousin, Ken, and Ken’s girlfriend, Diane. They are enjoying a light moment in the midst of darkening tragedy. Ken, driving drunk, has run over a pedestrian and fled rather than notify the police. The victim has turned out to be a gangster.

Kohl has gone along with the cover-up out of loyalty to Ken, a childhood playmate who took him in after Kohl’s parents died and he lost the family farm in Illinois. Now, in the bar, Ken tells Diane jokingly about how Kohl, on a high school football team called the Lions, was twice named Most Valuable Lion, and we hear an unexpected note:

“As (Kohl) remembered those brisk Friday nights under the lights, there was only one lion out on that field, and it was fear : fear of the coach and the crowd, fear of failure, and fear of success--fear of life finally.”

Later, when the bodies--including Ken’s--have begun to pile up, we hear it again:

“(Kohl) was only now beginning to understand what Ken’s death meant for him. . . . There was no one left now who really knew him. . . . (He realized) how totally alone he was, how bereft of his own life, his own past. . . . And he suddenly understood the old men who sat in bars talking at each other, never listening, pathetically trying to unburden themselves of histories known only to them, tales they would have to take to their graves.”

Such sensitivity and insight don’t usually come in the same package with a guy who can harvest corn, build houses, overhaul diesel engines, pilot a boat and single-handedly dismantle an underworld empire, but the combination isn’t new for Thornburg, who demonstrates again what good reading can be found on the border between genre literature and the real thing.

Thornburg’s specialty is to have a relatively innocent person stumble across a crime. In “To Die in California,” a farmer refused to accept that his son’s death was an accident. In “Cutter and Bone,” a bitter Vietnam veteran and his womanizing pal pushed their pursuit of a murder suspect to the point of obsession, tainting themselves in the process. Elements of both plots are recycled in “The Lion at the Door.”

For most of this novel, Thornburg’s border-straddling pays off. Along with the swift prose and guaranteed action of the suspense genre, he gives us vivid descriptions of Seattle and the Midwest and some acute and nasty commentary on how blue-collar workers went broke during the ‘80s while yuppies flourished. He has a good ear, too: Rural tycoons, black go-go dancers and Mafiosi all speak in convincing voices.

The major characters are satisfyingly complex. If Ken weren’t handsome but weak; if Diane weren’t smart but cold; if Bobbi, the cocktail waitress who witnessed the cover-up, weren’t flaky but country-shrewd--in fact, if the bumpers on Kohl’s pickup truck weren’t extra stout--the plot couldn’t advance as it does. Yet everyone has valid personal reasons for his behavior, so that plot seems to grow out of character as much as the other way around.

Only toward the end does this balance wobble. If Kohl weren’t decent, he wouldn’t stick by Ken; if he weren’t big and strong, he wouldn’t be able to avenge him. But even the beefiest ex-farmers aren’t likely to win repeatedly in hand-to-hand combat with professional thugs. It isn’t Kohl’s down-home grit that propels him through his final heroics, but the runaway machinery of the plot.

This may be a sign that Thornburg is getting bored with his specialty, careless about its demands or impatient with its limitations. Kohl is too nice a guy for the bloody task he is given; the price we pay for the excitement of the genre is to have him turn into a fantasy figure for a while.

It’s not a high price, in a novel as skillful and intelligent as this one. But it does make us wonder which side of the border Thornburg is going to work on next time.