The recent lighthearted improvement in A. M. Stein's Bagby series continues, with enough laughs here (though fewer than in Guaranteed to Fade, 1978) to offset the obviousness of the guilty party. So see-through is the crime, in fact, that Bagby doesn't let it occur till halfway through. First comes a semi-comic Fifth Ave. hotel robbery, Bagby taken as hostage along with a beautiful chic stranger and his mother's oldest friend, elegantly verbose Alexandra. (About the robbers' stocking masks she says, ""It speaks to what they are. . . they are devoid of even rudimentary taste."") Not only do the three hostages survive, however, but the svelte stranger falls for one of the robbers--a sweet would-be painter--and marries him after he gets out of prison. When this fellow is soon killed, suspicion falls on his confederates, with the missing loot as motive. But not really, of course. Pleasant, and only--in the final third--a trifle plodding.