King of the Rocket Men - 1949 Serial Ep 07 Molten Menace

King of the Rocket Men is a 1949 12-chapter movie serial from Republic Pictures, produced by Franklin Adreon, directed Fred C. Brannon, that stars Tristram Coffin, Mae Clarke, Don Haggerty, House Peters, Jr., James Craven, and I. Stanford Jolley.
An evil genius of unknown identity, calling himself "Dr. Vulcan" (heard only as a voice and seen as a mysterious shadow on a brightly lit wall), plots to conquer the world. He needs to first eliminate, one by one, the members of the Science Associates, an organization of America's greatest scientists.