Book #1 in the Mischief in Moonstone Series:

When her pet reindeer, Rudolph, is stolen from the live animal display, first-grade teacher Crystal Hagan has a big problem on her hands. Her students fear that Christmas will be canceled. Ironically, the prime suspect is a man who lives in a mansion known as the “North Pole.” And to her shock, Peter LeBarron admits to kidnapping Rudolph and he won’t give him back without some romantic “negotiations.”