Ian and Barbara are accidentally taken into Smithers' laboratory and, while the Doctor and Susan face a hazardous journey to reach them, they witness the deadly effects of DN6 first hand.
Did You Know?
This episode takes place in England in 1964. See more
The studio lighting is reflected in the rim of the plug hole on which the Doctor and Susan are resting See more
[separated from the Doctor and Susan, Ian and Barbara find themselves in a laboratory
Look at those enormous test tubes!