A flooded river threatens to sweep away a bridge construction project. Ranger Corey Stuart and Lassie brave the raging waters in a small boat to construct a log chain barrier and control the flow of water and logs.

A bloodhound needs to be relocated, but he dislikes all his new abodes.

Corey and another ranger battle a spruce bud worm infestation by spraying but meet resistance from a horse ranch owner. Lassie makes friends with a colt and reveals the true cause of death of one of the horses.