12 year old Jimmy Dubson meets a young bear named Dudley in a circus, where he's used for a clown's performance. The two become buddies and Jimmy tries to rescue Dudley. Beer handler Charlie has tells Jimmy that he can travel back to the year of 1870 through a magic cave in Grizzly Mountain. But after Jimmy arrives, it appears Dudley got lost during a panic. He then meets the native American Tukayoo and mountain man Jeremiah who will try to help him release Dudley in the wild. But that has be done before sundown, or Jimm will be stuck in 1870 for ever.