Inspired by the Christmas favorite Prancer, Gloria (10, raised in the UK) and her recently widowed American grandfather, Bud, befriend a mysterious reindeer. The extended family has gathered at Bud's rural northeastern home for Christmas and to decide where the cantankerous senior will spend his final years. When Bud comes to believe that the mischievous Prancer might actually be magical and Gloria fears that this will seal his fate to a retirement home. She helps keep his theory secret from the family while the unlikely pair unravel why Prancer has appeared, healing longstanding rifts in the family along the way.