Lassie - Episode #365 - "Mountain Mystery" - Season 11, E. 13 - 12/06/1964,

Ranger Cory gets sick drinking from a mountain stream, and Lassie helps the Forest Service find the poison source of the pollution, but becomes deathly ill in the effort. NOTE: Lassie and the Lassie Trademark are owned by Dreamworks Animation LLC. This episode was publicly broadcast in April 2016 via free over the air (OTA) antenna TV by COZY TV, an NBC affiliate. Recorded, edited to add titles, ending credits, and copyright information, and uploaded by Collie Lover to YouTube with no remuneration whatsoever. All YouTube pre-video advertisements are authorized and placed by Lassie copyright owner