Voyage to the Bottom of the Sea

Monster from the Inferno (3x1)

Air date: Sep 18, 1966

Seaview is investigating a thousand-mile wide communication blackout. The source of this is a large alien brain found under the sea. It is brought aboard and takes over visiting scientist, Dr. Lindsay. With his help, and after possessing Captain Crane, the alien vows to take over the Seaview and after that, the Earth.