Winner of the John Creasey Prize for Britain's best first crime novel of 1979, Serafin's debut is weak on plot--the predictable uncovering of a conspiracy in post-Franco Spain--but strong on gritty police-procedure and convincing Madrid atmosphere. The hero is Supt. Luis Bernal--an aging, wry Madrid police detective--who investigates the fall-from-a-window death of a young journalist. Suicide is the first impression, but Bernal suspects murder, especially when the journalist's dancer-girlfriend is soon also found dead. The main clue: the journalist's scrawled words ""Saturday of Glory""--which seem to refer to a planned pro-fascist demonstration on Easter Saturday. Is a Francoist coup in the works? And why is Bernal's boss so antagonistic about the investigation? The answers are obvious almost from the very start. But the supporting characters (especially the detective squad's new female rookie) are diverting; Bernal is an engagingly downbeat sleuth, with a clever mistress and a lugubriously old-fashioned wife (a disastrous cook reminiscent of the detective's wife in Hitchcock's Frenzy); and, with an array of knowledgeable backstreet locales, this could be the beginning of a distinctive Madrid series. . . if Serafin can come up with some fresher puzzles than this one.