Hopalong Cassidy (William Boyd), with his sidekick Lucky Jenkins (Rand Brooks) , accompanies California Carlson (Andy Clyde) when he leases the Bar-20 ranch, to claim his inheritance from a cousin. There are five heirs, one a young girl, Ruth Baxter (Patricia Tate). A mysterious, hooded stranger stalks the ranch property and one of the heirs is killed. Lucky saves Ruth from a similar fate and also discovers oil deposits on the property. Hoppy discovers the identity of the murder and also solves the mystery of the hooded strange with the help of the housekeeper, Matilda Hackerr (Una O'Connor).
—Les Adams <longhorn1939@suddenlink.net>