River Doon near, Alloa, Scotland
Full titles read: "THE MUSSEL'S SECRET."
L/S and M/S of a man standing in a lake looking through a glass bottomed box in his search for mussels. The narrator explains that inside the shell of the mussel are Doon Pearls. Several shots of the man. C/U of the man picking out a mussel from the lake with a pair of tongs. M/S's of and C/U of a man opening his catch, the second mussel he opens has a small round pearl inside.
Amendment May 2011:
Mrs. Hutt wrote in to explain that this is Alloway, not Alloa, and that The Doon is in Ayrshire.