There’s a moment in this episode when a gas knocks out most of the people in the village. The Doctor revives the Brigadier, and the Brigadier refuses to believe he was asleep on duty.
This is the last serial to feature the Brigadier for a while. I’m gonna miss that guy.
But Sarah Jane won’t miss the Zygons. They seem to keep coming after her. The first time was at the end of Episode One. Fortunately, she hadn’t hung up the phone, so the Doctor heard her screaming and rushed off to help with Sergeant Benton. They arrive at the hospital where the world’s least helpful nurse explains Sarah Jane left and Harry disappeared. A search of the building has the Doctor finding Sarah Jane in the decompression chamber. But when he goes inside, someone locks the door behind him and starts to deplete the air.
Fortunately, the Doctor knows some hypnotic techniques to keep himself and Sarah Jane from breathing too much (huh). And even better, Benton shows up to open the hatch. That leads everyone back to the Brigadier’s temporary HQ where everyone was unconscious. Stupid previously-mentioned gas attack…
But now the Doctor is suspicious. He figures, correctly, that they’re being watched. Furthermore, a local finds an alien tracking device.
Now might be a good time to say where Harry went. The Zygons kidnapped him. They have a submarine base, and they’re looking to rule the world. Why not? Everybody else wants that. Not me, though. Too much paperwork. The Zygons are aliens (duh) who crash landed on Earth ages ago. They were waiting for a rescue pick-up, but their homeworld no longer exists. I hate when that happened. They do have a cybernetic sea monster, and they are looking to take over the world.
Of course, if you are like me and I know I am, you’d probably be thinking one sea monster in a single Scottish lake won’t be enough. And you’d be right. But the Zygons can also impersonate people they’ve captured and opt to use Harry that way. A Zygon Harry can then take out Sarah Jane while the sea monster can maybe eat the Doctor. These guys figured out pretty fast who their real threats are.
As it is, Sarah Jane evades FakeHarry enough to drop him off the upper level of a barn. He dies and reverts back to Zygon form. Too bad the body is gone by the time Sarah Jane returns with UNIT soldiers to get the thing.
That said, the Doctor might be in real trouble. The tracker is stuck to his hand, and that monster is chasing him all over the dang place with no sign of help from anyone.