A PI performs some fancy footwork to protect Fred Astaire as "Edgar winner Kaminsky effortlessly choreographs Hollywood history . . . and dirty doings" ( Publishers Weekly).   Sometimes fools must step in where Fred Astaire fears to tap.   Luna Martin, the moll of a well-known Los Angeles gangster nicknamed "Fingers" (because he likes to cut them off), has demanded dance lessons from Hollywood's finest hoofer—and whatever Luna wants, Luna gets.   To sidestep the flirtations of the lead-footed lady, Astaire hires private investigator Toby Peters to pose as a dance instructor and take over the lessons. But when someone cuts in and cuts Luna's throat, the grieving gangster makes Peters an offer he can't refuse: Find the killer—or go from having two left feet to one foot in the grave.   Now, instead of punishing the parquet, the silver screen's most famous song-and-dance man is pounding the pavement with his new partner—a rumpled, middle-aged gumshoe who just wants to live to shuffle through another day . . .