The Doctor and Mrs Wibbsey are kidnapped by menacing robots and transported through a wormhole to an extravagant palace, floating in space, a hundred thousand years in the future. A colony of humanoid robots have overthrown their creators and forged a longstanding galactic empire. But now the humans are threatening to overthrow their Robotov Tsars. In an attempt to bring peace, the Tsarina creates Alex, a cyborg infant. And at his heart is a deadly Skishtari Egg.
Wibbsey and the Doctor traverse the wormhole back to Nest Cottage. But Nest Cottage hasn't been built yet. This is Hexford Village in the year 1861. And the TARDIS is a century and a half in the future. They also discover a thirteen-year-old boy with a paper face. And his favourite toy is the powerful Skishtari Egg.
Alex, Wibbsey and the Doctor have been pulled within the Skishtari Egg. Now they find themselves trapped in Aladdin's Cave, a labyrinth of magical rooms and strange characters.
The Doctor is reunited with his TARDIS and uses it to return Alex and Boolin to the Robotovs. Mrs Wibbsey is back at present day Nest Cottage, with the Skishtari Egg buried deep beneath it, as it always has been. While the Doctor is away, nine months quietly go by for her. Then Mike Yates returns, along with his former employers, UNIT, on the trail of alien activity. Mike has also teamed up with a strange little man claiming to be the Second Doctor.
The Skishtari spaceship failed to find their precious Egg and in the process, the entire village of Hexford is accidentally thrown through a wormhole and dumped on a barren moon in a strange galaxy. For three months, the villagers cope, with only Captain Yates and his mysterious, mop-topped little friend to maintain order. But the Robotovs' guards are closing in, as are the Skishtari. Finally, the TARDIS tracks down the misplaced hamlet. The Fourth Doctor and Mrs Wibbsey make their final confrontation, bringing with them the Skishtari Egg, just as it is about to hatch.
This story is a sequel to Hornets' Nest and Demon Quest, with the Fourth Doctor, Yates and Mrs Wibbsey reuniting. Serpent Crest begins by picking up from the cliffhanger at the end of Demon Quest.
The visiting Doctor recalls his adventures with the CybermeninThe Invasion and The Tomb of the Cybermen, the YetiinThe Web of Fear and the giant crabs in The Macra Terror. He also mentions an encounter with the Daleks in the diamond mines of Marlion, as mentioned in the Paul Magrs novel Verdigris.
Tsar Wars is the only story in all of the Nest Cottage series to contain no narration.
Tsar Wars reunites the cast of the 1971 film Nicholas and Alexandra, in which Michael Jayston had starred as Tsar Nicholas II of Russia and Tom Baker co-starred as the mad monk Grigori Rasputin (a role which was influential in Barry Letts' decision, in 1974, to cast him as the Fourth Doctor).
Michael Jayston previously appeared in Doctor Who in 1986, playing the Valeyard in the 13-part television serial The Trial of a Time Lord.
