Taming a Seahorse by Robert B. Parker

Nice girls don't. But blond, beautiful April Kyle does. She's a hooker hooked on the wrong guy -- and she's on her way to trouble. So is Spenser.
Looking out for April has landed him in the crud of Times Square. It's not a long way to big-business boardrooms where blood money get laundered into long green, sex is a commodity, and young girls are the currency.