Son of Lassie was released theatrically on April 20, 1945, by Loew's.In Yorkshire, at the estate of the Duke of Rudling (Nigel Bruce), the British Army converted the grounds into a training camp for war dogs.

The camp is placed under the supervision of Sam Carraclough (Donald Crisp), the kennel caretaker, who immediately begins the process of selecting the best dogs for training, including Laddie, the young pup of the champion collie, Lassie.

Laddie, being considered as a "war dog", follows Joe to training school and then stows away on his master's bomber, just as it takes off on a dangerous mission over Nazi-occupied Norway.

In his search for Joe, who is forced into a labor detail on a coastal gun emplacement, Laddie is reunited with his master and thereafter the two race for their lives to reach friendly lines as the Nazis pursue them.

[2] Principal filming took place from May 22 to mid-November 1944, in various locations throughout western Canada, including Vancouver Island and Christopher Point in British Columbia and Banff National Park in Alberta.

[7] According to The Hollywood Reporter, John Charles Reed sued MGM in October 1947 for plagiarism, claiming the film script was based on his 1943 story "Candy".

"[13] Variety characterized the principal actors as "excellent" but the film was "sticky sentiment, and flamboyant adventures, carry[ing] sufficient interest to move it along.