Victorian London is not a great place to be if you're a wounded shape-shifting alien.
Your ship is at the bottom of the English Channel, your crew are probably dead, and your nearest source of food is in a Loch six hundred miles away.
And the natives are insane.
Life isn't looking too promising for a Zygon called Bobby.

Sir Frederick Matravers Clive Merrison
Doris Kerry Skinner
Jethro Nigel Peever
Toby Anthony Keetch
Demeris ?

plus special guest star
Deborah Watling