Murder Takes Patience by Giacomo Giammatteo

A maniac killer—“Mr. Clean”—is on the loose in Brooklyn, and he’s targeting couples in the midst of making love. He finds them in hotel rooms, in their apartments, and even in the park. What he does to the victims is unspeakable, but afterward he takes his time cleaning the scene of evidence. With few clues to go on, Frankie and his partners are baffled—at first. But when Frankie and Lou start to close in on the killer, he turns his attention to them.