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 (Jon Pertwee) and Jo Grant (Katy Manning) 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 reptiles intent on eliminating humankind and reclaiming the Earth for themselves. Extras include commentary by director Michael Briant, producer Barry Letts, and script editor Terrance Dicks, and enough bonus featurettes to please even the most dedicated fans of Doctor Who.