Drs. Nancy Vincent and Arthur Loring take vacation from their academic medical careers in Minneapolis and embark on a wilderness canoe trip the Minnesota-Ontario Boundary Waters. Their idyllic adventure is interrupted by an out-of-control forest fire that pursues them as they make their way south up the Magnetic River to Gunflint Lake. Forestry service planes pass overhead as they drop water on the advancing blaze.

Crossing the lake and reaching Gunflint Lodge, they set up a medical aid station for injured fire-fighters at the resort. Their medical skills are welcomed by men returning from the fire and needing aid.