I den lille mineby Greenhall Bridge i det idylliske Yorkshire bor den ni-årige Joe Carraclough sammen med sine forældre, Sam og Sarah, og deres elskede og kloge hund, Lassie. Anden Verdenskrig raser for alvor, og den lille familie kæmper en brav kamp for at holde elendigheden og sulten for døren. En dag, da Joe og Lassie følger med i en lokal jagt, får den magtfulde hertug af Rudling og dennes steddatter, Cilla, øje på Lassie, og Cilla bliver meget begejstret for den smukke hund. Hertugen af Rudling tilbyder da familien Carraclough at købe Lassie, men den lille familie er under ingen omstændigheder indstillet på at sælge Lassie.

Hard times come for the Carraclough family and they are forced to sell their dog, Lassie, to the rich Duke of Rudling. Lassie, however, is unwilling to remain apart from young Carraclough son Joe and sets out on a long and dangerous journey to rejoin him.

Shell-shocked Barbara must face up to the loss of a dear companion after a tragic accident. Her best friend Klara and husband Torsten devise a plan to thaw Barbara's heart, after she reminisces about the incident, the funeral, and happier times. Will she agree to the suggestions of her nearest and dearest? Can grief turn into hope?

The story of the rough collie hero, Sunnybank Lad.