The Sea Devils

STORYLINE

The Doctor and Jo Grant visit their old enemy the Master, who is the sole inmate of a top-security prison on a remote island off the south coast of England. Local shipping has been plagued by a series of tragic accidents and several ships have been lost. Joining forces with Captain Hart of the HMS Seaspite naval base, the Doctor learns that there have been garbled reports of sea monsters. Colonel Trenchard, Governor of the Master's prison, believes that the ships are being attacked by enemy spies. The Master himself seems to be a reformed man and claims to have turned away from his life of crime.

Nothing could be further from the truth. The Master has in fact made contact with the Sea Devils, aquatic cousins of the prehistoric Silurian race encountered by the Doctor some time ago. Having slept beneath the sea for millions of years, the Sea Devils have awoken and intend to reclaim what they consider to be their planet.

Aided and abetted by the evil Master, who will stop at nothing to take revenge on those who imprisoned him, the Sea Devils plan to eliminate the human race, a species they regard as nothing more than upstart apes...