Note: This story was only released separately in the US. In the UK and Australia it was released as part of the Beneath the Surface box set instead.
Exiled to Earth and now working for UNIT as their scientific advisor, the Doctor is summoned to an underground research center at Wenley Moor to investigate a series of inexplicable power losses. Initially suspecting sabotage, he soon discovers that the nearby cave system conceals a colony of an ancient race called the Silurians. Awaking from a hibernation which has lasted millions of years, they are now planning to reclaim the Earth from humankind.
DVD EXTRAS INCLUDE:
- Commentary by actors Caroline John (Liz), Nicholas Courtney (The Brigadier), Peter Miles (Lawrence), Geoffrey Palmer (Masters), director Timothy Combe, producer Barry Letts, and script editor Terrance Dicks
- What Lies Beneath Cast and crew explore how the socio-political climate of the late sixties shaped this story (35 mins)
- Going Underground Making Of (19 mins)
- Now and Then Location featurette (9 mins)
- Musical Scales Retrospective on an era of musical experimentation in Doctor Who (13 mins)
- Color Silurian Overlay Featurette showing how the story was restored to full color for DVD release (4 mins)
- Isolated Music
- Radio Times Listings (DVD-ROM PC/Mac)
- Photo Gallery (6 mins)
- Production Note Subtitles
- Digitally remastered picture and sound quality
Originally transmitted January 31 - March 14, 1970