Double Scotch - The Erin O'Reilly Mysteries, #4

Two killers are prowling Manhattan. It's double duty for Erin and RolfA detective doesn't always have the luxury of giving all her attention to just one case. Erin O'Reilly and her K-9 partner, Rolf, have just started to sink their teeth into their latest investigation-a pair of Scottish gangsters, tortured, executed, and washed up on the rocks-when another mystery intrudes. A beautiful young woman is found dead in a locked hotel room, posed with a bouquet of fresh roses.
It looks like a carefully staged suicide, but Erin isn't so sure. Soon she's juggling two cases at once, dodging bullets in a budding mob war while trying to nail down a cunning serial killer-one who just might be stalking her in return.