Dated to the late Stone Age, Stonehenge may be the best-known and most mysterious relic of prehistory. Every year, a million visitors are drawn to England to gaze upon the famous circle of stones, but the monument's meaning has continued to elude us. Now investigations inside and around Stonehenge have kicked off a dramatic new era of discovery and debate over who built Stonehenge and for what purpose. How did prehistoric people quarry, transport, sculpt, and erect these giant stones? Granted exclusive access to the dig site at Bluestonehenge, a prehistoric stone-circle monument recently discovered about a mile from Stonehenge, NOVA cameras join a new generation of researchers finding important clues to this enduring mystery.

Astronauts rescued from a mission to mars are kidnapped when they arrive back on earth. They seem to have been irradiated, and can now kill people merely by touching them. But the Doctor discovers the astronauts have been replaced with Alien ambassadors who are being forced to behave in a hostile manner. With The Doctor traveling to the alien mother ship, and Liz kidnapped, The Brigadier is left wondering who to trust.

The TARDIS narrowly avoids becoming engulfed in a cobwebby substance in space. It arrives in the London Underground railway system, the tunnels of which are being overrun by the web and by the Great Intelligence's robot Yeti. The time travellers learn this crisis was precipitated when Professor Travers, whom they first met in the Himalayas some thirty years earlier, accidentally caused one of the Yeti to be reactivated, opening the way for the Intelligence to invade again.

The adventures of The Doctor, a time-traveling humanoid alien known as a Time Lord. He explores the universe in his TARDIS, a sentient time-traveling spaceship. Its exterior appears as a blue British police box, which was a common sight in Britain in 1963 when the series first aired. Along with a succession of companions, The Doctor faces a variety of foes while working to save civilizations, help ordinary people, and right many wrongs.