Joshua Ferris’s second novel is a good one striving to be great. Posing the question of what might happen to a comfortable, complacent man stricken with a bizarre and inexplicable condition, it never quite runs to ground any central theme, leaving instead a story that has moments of unaffected poignancy, but in the end drifts off with the wispiness of smoke.

Forty years ago, Tim Farnsworth would have been a character in a Louis Auchincloss novel. A respected litigation partner in a large midtown Manhattan firm, he is immersed in preparing the defense of a client who controls $20 million of corporate business and now faces conviction for the murder of his wife. In the midst of what should be intense trial preparation, Tim is stricken by a mysterious ailment that recurs in four-year cycles and compels him to walk to the point of exhaustion (his early treks evoke Neddy Merrill’s frantic journey across Westchester County in John Cheever’s “The Swimmer"). “Not an occult possession but a hijacking of some obscure order of the body,” as his wife Jane thinks of it, “the frightened soul inside the runaway train of mindless matter, peering out from the conductor’s car in horror.” When he awakens in the early morning hours in a potato chip truck or curled up next to a Safeway dumpster, Jane, herself a successful real estate broker, leaves their comfortable suburban home to rescue him.

Adorned with every totem of success, Tim’s outwardly perfect world quickly unravels. His partners (sketched with dark humor and the insight of a marine biologist assaying the occupants of the shark tank) no longer can tolerate his abrupt departures and remove him from the trial team and eventually the firm. In desperation, Jane handcuffs him to a hospital bed in their home, and details their daughter Becka, an overweight and disgruntled teenager who aspires to a career as a folksinger, to sit by her father’s bedside watching endless hours of “Buffy the Vampire Slayer” DVDs. “If he just had an expiration date,” Jane reflects of her decision to leave Tim in Becka's care, “of course she’d sit with him.” Dr. Bagdassarian, the physician Tim “disliked the least of all his doctors,” admonishes Jane, “Try your best that he doesn’t forget what it means to be human.”

Tim’s futile search for a cure to what one doctor describes, with unhelpful literalism, as “benign idiopathic perambulation” culminates when he shaves his head and dons a device that looks like a bicycle helmet designed to measure his brain waves. Bereft of hope, he eventually abandons what once was his well-ordered life to embark, in a “brain fog,” on a pedestrian ramble from New Jersey to the West Coast.

After its increasingly grim account of the physical and emotional toll of Tim’s westward journey, there’s an undeniable power, even eloquence, to the concluding 50 or so pages of the novel, retracing his return trip in the face of Odyssean obstacles across America (the focus more on its varied, storm-blasted and sun-streaked landscape than its people) to reunite with Jane: “The path itself was one of peaks and valleys, hot and cold in equal measure, rock, sedge and rush, the coil of barbed wire around a fence post, the wind boom of passing semis, the scantness and the drift.” Their intense devotion, especially Jane’s desperation (expressed in a moving scene in a roadside diner when Tim offers her both love and freedom with a chilling “I don’t want you”), reveals the tensile strength of the bonds that hold couples together in long-term relationships.

THE UNNAMED fails to fulfill its bright promise, not from some complacency that might be understandable in an author fresh from the enormous success of his first novel, but instead owing mainly to the lack of clarity in articulating a compelling vision. Choosing to dangle a multiplicity of explanations for Tim’s plight --- from the hollowness of success in contemporary America, to the limitations of medical science, to the mind-body dichotomy, to the challenge of religious belief --- Ferris ultimately abandons the reader to the same uncertain fate. Like Tim, we long for “some measure of understanding, some small answer that might stand in for the clarification of all the mysteries in the world.” Perhaps that murkiness was a conscious choice, and while it may inspire many animated book club discussions, it feels less an act of courage on the author’s part than a failure of will. Obscurity, even in the name of art, is no virtue.