A Victorian era scientist and his assistant take a test run in their Iron Mole drilling machine and end up in a strange underground labyrinth ruled by a species of giant telepathic bird and full of prehistoric monsters and cavemen.

A Victorian scientist and his young American backer set off in their new earth-boring machine with a short test on a Welsh mountain. Unfortunately the thing is rather more powerful than expected and they end up in an enormous cavern at the centre of the earth. Here they find a race of humans enslaved to evil oversized prehistoric birds with extra-sensory abilities. The travellers decide they can be some help, the more so as at least one of the slaves is very eye-catching.—Jeremy Perkins {J-26}