A modestly amusing return for Simon Bognor of Britain's Board of Trade--in a less farcical, steadier case than his last, Just Desserts (1979). Now finally wed to his perennial fiancÃ‰e, Monica-the-blasÃ‰, the sleuth is getting on (""Bognor in early middleage was not a pretty sight""). But, in Toronto to investigate a case of LSD-smuggling (in ""Gentleman's Relish""), Bognor shows his usual curiosity when tycoon Sir Roderick Farquhar is found dead in the bathtub of his private railroad car (phosphorus trioxide in the bath oil). The prime suspect? Sir Roderick's secretary--a radical Quebecois nationalist. But Bognor quickly spots many other possibilities: Sir R.'s son-in-law, who was about to be booted out of the company; Sir R.'s ex-wife, who wanted to remarry but didn't want to lose her alimony; assorted husbands whom Sir R. had cuckolded (including a leader of Canada's Liberal party). And it's clear that Bognor is hot on the trail--because he's soon threatened and severely roughed up (while skiing). Finally, however, after a brief flirtation with a suicide theory in London (Sir R. was terminally ill), Bognor jets back to Toronto for a showdown with the not-very-convincing culprit. Fair plotting, engaging manner--a spry, not-too-silly outing for mystery-comedy fans. . . with an extra attraction in the unhackneyed Canadian locale.