Time-traveler plans to ensure Harold's victory at Battle of Hastings.

Jamie and Peri aid the Doctor.

Chessene attempts to travel through time without the Rassilon Imprimature.

While in Victorian-era London investigating oddities such as spontaneous combustions and a dinosaur in the Thames, Clara struggles to know the man the Doctor has become.

The Doctor comes to the rescue of a lone rebel ship that is surrounded by a Dalek fleet.

Set in Wales, in the not too distant future, the Doctor is finally able to pay Metebalis Three a visit. Meanwhile, several mysterious deaths in the same vicinity of the Global Chemical's plant lead to suspicion regarding the effects of toxic waste.

During the Doctor's visit to Metebelis Three, Jo and UNIT dig deeper into the investigation near the Global Chemical's plant. Are the deaths and wildlife deterioration directly linked to the company's waste?

In an attempt to neutralize the potential of the virus spreading, Doctor Who ingeniously extracts an egg out of the mine. In doing so, he hopes to isolate the virus and decrease the chances of it coming into contact with anyone.

After Doctor Who extracts an egg out of the mine to neutralize the virus, Stevens gives commands to Brigadier to close the mineshaft up with explosives in an attempt to seal everything inside completely.