Tourists Are for Trapping

British public relations partners Doug Perkins and Gerry Tate make a third appearance here, called in to soothe the disgruntled American tourists on Larkin's Luxury Tour #79. It seems that one of the group, an elderly math professor, died accidentally while the tour was in Zurich. Meeting the travelers in London, Perkins finds them edgy, morose and in a state of collective shock. Then he discovers that the professor's death was a murder, and that the tight-lipped group is staging a conspiratorial cover-up. When another member disappears, Perkins's troubles multiply. Fattened with unrelated subplots, this sluggish book springs to life only in the last few pages when Perkins intuitively divines the reasons behind some nefarious deeds. But neither Perkins's irrepressible good humor and staunch perseverance nor the antics of his spirited cat Pandora are enough to salvage this lackluster story, doomed by pallid characters and a low-key, never fully developed mystery. (Dec.)