June Lockhart (Ruth Martin)Hugh Reilly (Paul Martin)Jon Provost (Timmy Martin)Robert Howard (Sergeant Sprague)Will J. White (Constable MacDonald)Richard Kiel (Chinook Pete)Walter Stocker (John Stanley)Walter Kelley (Control Tower Operator)Patrick Waltz (Pilot)Leo Needham (Ranger Henty)Lassie (Lassie)Dick SimmonsPatrick Westwood
While in Canada Timmy and Lassie encounter a downed hot air ballonist. By accident they end up in the balloon which takes them into the wilderness. The young boy and his dog must find a way to survive even fending off a wild pig.