Elizabeth Strout’s batting average now qualifies as dazzling — with reason. Each new title seems only to refine and distill the Pulitzer winner’s already gorgeous skills. You know you’re in expert hands when a novel’s first lines chop a clean stroke straight to its own heart: “Grief is such a — oh, it is such a solitary thing; this is the terror of it, I think.”

Oh William!” investigates those timely themes — loneliness, grief — in such a rich, mesmerizing narrative, I devoured it greedily. It is told by Lucy Barton, who appeared in the collection “Anything Is Possible” and the novel “My Name Is Lucy Barton,” (which became a one-woman play starring Laura Linney). In “William!” Lucy’s now a hugely famous writer (apparently a still-feasible category) grieving the recent death of her second husband. But it’s not the deceased who’ll take center stage.

“I would like to say a few things about my first husband, William.” Tracing Lucy’s history with him while the two try to solve a dark mystery, “William!” intricately interleaves past with present.

As Lucy describes William — an aging parasitologist (make of that vocation what you will) who has, post-Lucy, married a much younger woman and had a daughter with her — I pictured a blend of the actors Max von Sydow and Sam Elliott. Tall, trim but for a “small potbelly you could barely see with his clothes on,” older but with good hair (“white now but full”), William is fit, taciturn, authoritative.

That last part will change.

William’s pursuing a story — or it’s in pursuit of him — that he scarcely understands. As he enlists Lucy’s help tracking down what will prove a painful family secret, we’re slowly immersed in what the two have — and lack — together: not romance, but something far deeper and more complicated. Lucy’s perceptions of her first husband vacillate in maddeningly recognizable ways. There’s tenderness: “A little bit, the sight of him . . . broke my heart. But [I had that feeling] almost every time after I saw him.” There’s anguish and anger: “At times in our marriage I loathed him. I saw, with a kind of dull disc of dread in my chest . . . a juvenile crabbiness, a scowl that flickered across his soul, a pudgy little boy with his lower lip thrust forward who blamed this person and that person — he blamed me.”

Lucy and William have two grown daughters, whose portraits are vibrantly drawn. Somewhat less visible is William’s daughter with his current wife, Estelle. But for all their dimension and drama (a miscarriage, sulks, confrontations) these daughters — and even Lucy’s expired husband — seem to function more as elements of a palpable backdrop against which Lucy and William may seek and repel each other, like magnets with reversing currents.

Yoked by an intense, shared past, their bond runs deep. When night terrors start plaguing William, Lucy marvels, “he would think of me . . . the fact that I was out there alive, right now . . . gave him comfort. Because he knew if he had to . . . that I would take a call from him.” Conversely, on discovering her late husband’s illness and at his death, “it was William I called first.”

So much intimate, fragile, desperate humanness infuses these pages, it’s breathtaking. Almost every declaration carries the force of revelation. Lucy wants to like Estelle but sours after glimpsing her murmur conspiratorially to another man, “Are you bored to death?” at a birthday party for William. It implies to Lucy that Estelle “herself was bored, and this was a thing I did not care for.” Strout imbues Lucy’s voice with a nervous defensiveness expressed in agitated stops and restarts: “Oh, I cannot say any more right now” or “what I am saying . . . ” or “What I mean is . . .” as she struggles to clarify.

Lucy’s wretched, abused childhood (not detailed here but implied) has never left her: “I have still never felt that I had a home.” Often she floats at a mental remove, “like I was [not quite] really there . . . I had it my whole marriage with [William] . . . a quiet horror that sat beside me . . . And we lived our lives on top of this.” And despite her great fame as an author, she feels invisible “in the deepest way.”

William also excels at absenting himself — through prior sexual affairs or just mentally — so much so that Lucy “wondered who William was. Many times I have wondered this.”

Still, it’s Lucy he asks to accompany him on a journey to understand a grim puzzle from his past — involving his late parents, who’d settled in Maine, one of whom was a German prisoner of war — with the help of latecoming players who’ll provide that story’s lost pieces. Yet for me these elements, too, form a field against which the strange dance of Lucy and William staggers forward. All do, however, fit snugly inside this narrative’s urgent argument — about love missed or withheld, and what that leads to — culminating toward the novel’s end in a stunning confession by Lucy.

To a degree, earlier pages prepare us for it. Describing an online site called Ijustwanttotalk.com, Lucy notes: “People are lonely, is my point here. Many people can’t say to those they know well what it is they feel they might want to say.”

“Oh William!” tries to say it for us.

Joan Frank’s newest novel is “The Outlook for Earthlings.” Recent works include “Where You’re All Going” and “Try to Get Lost: Essays on Travel and Place.”

Oh William!

By Elizabeth Strout

Random House. 256 pp. $27