In 2084AD The Doctor, Tegan and Turlough land on Sea Base 4 just as it comes under attack from the Silurians and Sea Devils; the original owner and masters of the planet Earth. With the threat of a nucleaer conflict that could wipe out the planet; will The Doctor be able to make peace between humanity and the prehistoric reptile; or will he have to revert to another way to save the Earth. Cast Peter Davison (The Doctor), Tom Adams (Vorshak), Nigel Humphreys (Bulic), Ian McCul

When a series of shipwrecks leaves no survivors, The Doctor realises an ancient race of aquatic creatures called the Sea Devils are responsible. After awakening from millions of years in hibernation, The Master plans to help the pre-historic monsters reclaim the Earth, and wipe out humanity. The Doctor, meanwhile, believes humanity and the Sea Devil can live in peace, but not everyone agrees. Cast Jon Pertwee (The Doctor), Katy Manning (Jo Grant), Roger Delgado (The Master),