Take one grand house, stuff it with staff, and make it home to several generations. If they send their sons to Oxford and occasionally knock each other off, you've got a country-house murder mystery, the delight of classic English crime fiction. But if the boys are at Yale, odds are that you're reading its American counterpart, the New York mansion mystery'a genre largely invented by Elizabeth Daly. In Arrow Pointing Nowhere Daly is back on the Upper East Side, where Gamadge has been receiving missives suggesting that all is not right at the elegant Fenway mansion.