Taking up a tradition that goes back at least as far as medieval morality plays, Russell Banks peoples his book with types: the Kid, the Professor, the Writer, the Shyster. And it is something of a morality play that unfolds in "Lost Memory of Skin."

The Kid, a 22-year-old registered sex offender recently out of jail and wearing an ankle monitor, takes up residence under a causeway on the Florida coast -- one of the very few places where he can stay in his county, as prescribed, yet more than 2,500 yards from anywhere that children frequent. Soon, he is taken up by the Professor, an enormous man of locally celebrated genius, who is making a study of youthful sex offenders attempting rehabilitation and makes the Kid his special project.

As the Professor interviews the Kid, and tries to help him, both men's stories begin to emerge, and the Kid's story, at least, begins to change. He is, we learn, the child of a promiscuous and neglectful mother, and, at 10, began to occupy himself with Internet pornography and never let up; his crime was arranging to meet a 14-year-old girl who'd flirted with him online. That he is a virgin makes his status that much weirder and somehow more poignant.

The Professor's life is, in many ways, a product of his own intellect. It has, we are told, "many distinct narratives." These narratives involve his work for various government agencies, some foreign, his political activism, real and assumed -- mole, spy, asset. How much of this is true we -- and the Kid -- can only guess. "If everything is a lie, nothing is," the Professor tells himself. "Just as, if everything is true, nothing is." It's a sentiment oddly echoed by the innocent and ignorant Kid, who late in the book remarks, "If everything's a lie, then nothing's true."

And there's the thing. Banks seems to want his characters to be types true to their monikers. The Kid, who knows nothing of culture, geography, history, current affairs, "is one of those people who have made up the mass of mankind since the species first appeared on the plains of Africa two or three million years ago."

The Kid, that is, is at heart a primitive. He is the story's id. And the Professor? The superego. How these two interact, through the incursions of outraged citizenry and catastrophic acts of nature, is interesting, a curious bit of choreography. But neither of them is altogether believable -- to a reader, or to Banks, who strains to give the barren emotional and intellectual life of the Kid the sort of reach and depth that have always made his writing so compelling.

Banks can't help himself. He wants to tell the story of a sad little sex offender and his equally pathetic worldly mentor; but he also want to tell the story of the depredations of civilization as enacted through the natural, cultural and political history of the Florida peninsula. And this requires the sort of density of insight and prose that distinguish Russell Banks' writing but are far beyond the vehicles he has chosen in this novel.

Novelist Ellen Akins teaches in the Fairleigh-Dickinson MFA program. She lives in Wisconsin.