Doctor Who and the Horror of Fang Rock — Terrance Dicks

On a remote rocky island a few miles off the Channel coast stands the Fang Rock lighthouse. There have always been tales of the beast of Fang Rock, but when the Tardis lands here with Leela and the Doctor, the force they must deal with is more sinister and deadly than the mythical beast of the past.

It is the early 1900's, electricity is just coming into common usage, and the formless, gelatinous mass from the future must use the lighthouse generators to recharge its system. Nothing can stop these Rutan scout in its search and its experimentation on humans...