Doctor Who (1963): The Doctor, Peri and Lang follow Edgeworth to Jaconda. They find it has been devastated by giant gastropods. And the gastropod leader, Mestor, is poised to launch a terrible plan…
Elisabeth Sladen, Frazer Hines, Jacqueline Hill, John Levene, John Scott Martin, Jon Pertwee, Katy Manning, Nicholas Courtney, Pat Gorman, Patrick Troughton, Peter Davison, Tom Baker, William Hartnell, William Russell
Adventure, Drama, Sci-Fi
Maybe also available here.