In a situation hopelessly vulnerable to puns, Rosie Dastgir’s first novel, A Small Fortune (Riverhead, $25.95), has been followed closely by her husband John Gapper’s own debut, A Fatal Debt (Ballantine, $26). The two novels, however, deal in two different currencies: In her psychologically complex story of cultural strains, family connections are skewed by money; in his intricately plotted thriller, lives are poisoned by specious financial derivatives.

“A Small Fortune” is set chiefly in present-day England among people of Pakistani descent. Harris (born Haaris) escaped life in Pakistan many years ago by marrying an Englishwoman and leaving behind the woman he had been contracted to marry. The worst sort of scandal had been averted at the time when his cousin Khalid Ali stepped up to marry the woman himself. He now lives in a poor village with his wife and children. As it happens, Harris’s bright prospects never really panned out, and his British wife, frustrated by his general inadequacy, finally divorced him. Since then, he has been living in the damp, decaying north of England — splendidly and dismally evoked by Dastgir — where he has been exploited by a relentless cousin named Nawaz. In exchange, Harris has become part of Nawaz’s family, which brings him companionship, excellent curries and an audience for the advice he is fond of dispensing. When the final settlement of his divorce brings Harris a check for over 50,000 pounds — a small fortune — he ponders its deployment. His daughter refuses it. She is living in London, also adrift, having dropped out of medical school. Harris laments that she has embraced “the English way of putting freedom and pleasure before family and duty.” But he is scarcely fit to pronounce so dogmatically on that subject. As the novel progresses in deftly evoked scenes and flashes of humor, Dastgir moves further and further into the man’s conscience, his reluctance to grapple with reality, and his very human knack of holding traditional convictions while letting them slide in his actions. When redemption comes, that small fortune plays exactly the proper role.

Meanwhile, some 3,500 miles away, 50,000 pounds is chump change in “A Fatal Debt.” Dr. Ben Cowper, a young psychiatrist at a Manhattan hospital, is treating a former Wall Street bigwig named Harry Shapiro. He was brought in by his wife, who believes the former executive is contemplating suicide. Until a huge portfolio of funds turned out to be worthless, Harry was the chief executive of a powerful investment bank, an institution with ties to the U.S. Treasury and the cultish loyalty of its alumni (think Goldman Sachs). Harry is now a broken man, though still a very rich one. As a past and potential donor to the hospital, he gets what he wants: to go home and engage Ben as his psychiatrist. But when Harry is accused of murdering the man who ruined his career, Ben is left holding the bag for releasing an unbalanced patient. As with the toxic assets that brought Harry down, so in this novel nothing is what it seems. Gapper’s ingenious thriller about the ruthless world of high finance and Dastgir’s story of family bonds make strange bedfellows, but their married creators have produced novels that readers can invest in with confidence.

Powers is a writer in Boston.

”A Fatal Debt: A Novel” by John Gapper (Ballantine Books/Random House)