Doctor Who: The Sea Devils

Arrested after the events at Devil's End, the Master has been incarcerated at a top security prison on a remote island off the south coast of England. When the Doctor and Jo Grant pay a visit to their old enemy, they find him a reformed character. But can the spate of mysterious shipping accidents and garbled reports of sea monsters in the local area really be a coincidence? The Doctor soon finds himself pitted against the Sea Devils, an ancient race of reptile intent on eliminating humankind and reclaiming the Earth for themselves.