To The Nines by Janet Evanovich

Stephanie Plum has a visa absconder to find or her whole bonds office is in jeopardy. The train for the missing fugitive leads from the New Jersey Turnpike, to the Las Vegas strip, to a group of killers who are giving new meaning to the word 'hunter'...

Stephanie could use some back up on this case, but her incredibly hot mentor, Ranger, has been 'asked' never to come back to Vegas. And when it comes to her cop boyfriend, Joe Morelli, sometimes it's better to let what happens in Vegas stay in Vegas.