Earlier adventures of unattached samurai, or ronin, Zenta and Matsuzo (The Samurai and the Long-Nosed Devils, White Serpent Castle, Valley of the Broken Cherry Trees) have been intricate and textured; so it's a disappointment to find that this could be classified simply as a samurai mystery. On a nostalgic visit to Ikken, Zenta's one-time mentor, the two find his village terrorized by a ""Vampire Cat,"" a dark-garbed, mewing creature brutally slaying young women. Chief beneficiaries are a band of medicine peddlers, who've been extorting money from the villagers for alleged anti-Cat potions. But they are mere accomplices, Zenta learns from the chief of the band; and the crazed ""Cat"" is not only after blood--he wants to get the money that Ikken's niece, Asa, will inherit from her rich merchant-grandfather. But why does Asa's canine protector Kongomaru keep going after Zenta? Except for some samurai/ merchant class frictions, the unraveling is just a matter of incidental swordplay and eliminating suspects--including of course Zenta. The culprit turns out to be Ikken's sword-master son, not killed three years back but hideously disfigured . . . and not only nursing a grievance against the villagers but loco about Asa, to whom he'd been engaged. In the wind-up, Ikken and son Shunken both commit hara-kiri, freeing Zenta and Matsuzo--more one-dimensional than in previous episodes--to go on to new challenges. Readers who've been caught up by the pair will probably go along for the action, but it's a thin whodunit overall.