Margaret Binton, that cigarette-smoking Miss Marple of Upper-West-Side Manhattan (The Rag Bag Clan, 1978), returns--in a leisurely, low-key charmer that manages to find an agreeable middle road between cutesiness and real suspense. The murder victim: sweet old Luiz Valdez, a Yankee Stadium groundskeeper who had started a community vegetable garden in a vacant city lot. The suspects: the five neighborhood teenagers who'd been working on the garden with Luiz and Margaret. The motive: a cache of stolen diamonds which the young murderer/thief buried in the cucumber patch (Luiz got suspicious when no cucumbers grew there). So Margaret--who finds the gems but keeps mum in order to smoke out the killer--sleuths around, at one point posing as a Hadassah fundraiser; and her investigation elicits attempts on her life: poisoned corn-bread, gas. Finally, however, after Margaret really panics the killer with her threat to plant a tree on the buried-treasure spot, there's some neat deduction and an unsurprising culprit. With nicely sketched characters and N.Y.C. backgrounds--a genial little pleaser.