Terror of the Zygons
By Robert Banks Stewart
“This one they call the Doctor is a threat to us. Already he has found out too much. He must be destroyed.”
Responding to the message from The Brigadier from the space/time telegraph he left him The Doctor, Harry and Sarah find them in present day Scotland. Apparently something is destroying oil rigs off the coast of Scotland and causing alarm as these rigs are huge and supposedly are unsinkable. The Doctor examines some of the wreckage that has washed ashore and found one particular piece of steel interesting. After using some plaster and making a mold The Doctor shows The Brigadier that the mold is of a giant tooth. What makes it impressive is that whatever is the owner of the tooth is strong enough to eat through steel as if it was paper.