Good news, Lathen fans: the lull is over. Yes, after the dismaying dullness of recent outings for Wall St. banker John Putnam Thatcher (who went astray amid international terrorists and athletes), the pseudonymous Lathen duo has returned to prime Thatcher territory: a family-owned business, with amusingly shaded personality-conflicts and dirty-dealings. The volatile firm here is Vandam Nursery & Seed Co.--a mail-order giant (a subsidiary of Standard Foods, a Thatcher client) that's about to make big news and big bucks with its latest offering: a biennial tomato that bears fruit for a full six months! But suddenly, just as the annual catalogues are about to go out, Vandam gets slapped with a lawsuit: a small rival company, Wisconsin Seed, claims that they developed the tomato first, that Vandam stole their research! So the tension mounts splendidly, with the focus turning from the squabbling Vandams. . . to the independent research team that did the Vandam tomato-project. . . to the abrasive Wisconsin guys (who did their own research). And caught in the middle of it all is secretary Barbara Gunn, who now works for Wisconsin but used to work for the Vandam research team: a sadly sympathetic character, she winds up poisoned at the Plant Society convention in Chicago. True, Lathen cleverly keeps us guessing by telling some, but not all, of the suspects' thoughts, until the end, you won't be quite sure who's been doing the stealing, bribing, and killing. But the mystery is only the minor attraction here. The distinctive appeal comes instead from the lightly satiric, selectively detailed textures: a quirkily engaging cast of greedy, quarrelsome merchant/scientists; a grand contingent of endearing supporting players; and a few choice commercial technicalities and wry observations from J.P.T. himself (with assists, of course, from that quintessential managerial woman, Miss Corsa). A thoroughly welcome return, then: Thatcher's back in commerce--and Lathen's back in business.