Most British attempts at hard-boiled sleuthing are anathema to US readers-painfully imitation-American or impenetrably dialect-ic--but Leigh's Sam Carroll is a plain, wryly effective narrator-shamus, working his seedy-London territory in matter-of-fact L.A. style. . . even if his case here winds down disappointingly. Taking pity on a pathetic would-be prostitute in Leicester Square one night, Carroll tries to befriend teenage runaway Charlene Storm--whose step-dad is a posh ad-man, whose mum is an unstable sort susceptible to gigolos. So, soon hired by Mr. Storm to deal with Mrs. Storm's latest, a bisexual gigolo/blackmailer named Carlos, Carroll finds the hustler murdered. . . with Charlene (following in mum's sleazy footsteps) in the adjoining bedroom. And though the hysterical Mrs. Storm confesses, Carroll investigates--zeroing in on the ""lonely hearts club"" for which Carlos worked--and comes up with a thin solution out of left field. (He also clears up, somewhat more satisfyingly, the truth about a long-ago murder in Mrs. Storm's past.) Still, despite the washout of a plot, Carroll--a tender/tough guy most reminiscent of Robert B. Parker's Spenser--is a welcome transatlantic arrival; and, with a stronger puzzle, he could turn into a major presence.