Harry Sullivan and Sergeant Benton–the real ones–both have their final appearances in this episode. They don’t do much, but that’s beside the point. Harry was a one-time companion who just showed up and stuck around for a bit. Benton has been a supporting character for a while now. Oddly enough, Captain Yates reappears a couple more times after this, but not those two guys.
As for the Brigadier, he isn’t in this episode, but he does come back for future Doctors and there’s a mustachioed officer to stand in for him in the meantime.
As for the Doctor and Sarah Jane, good news: the G-Forces do not crush them to death. Sure, they might very well die before the pods land them back on Earth, but the G-Forces won’t kill them. This time. So, there are no more problems, right? They can just slip back to Earth, warn UNIT, and stop the Kraal invasion.
Oh crap. There’s an android copy of the Doctor.
Problems erupt when the android pods go down to Earth on their own. Sarah Jane finds the TARDIS and the Doctor. But he seems a little weird. And stiff. And he has another Sarah Jane with him.
She makes a run for it.
The Doctor does get into UNIT HQ, maybe just in time to warn everybody. But then the androids show up and start replacing people, including Benton. The Doctor does manage to get a schematic to a radar tech that will turn off the robots. All he needs is time.
And then he learns the mustachioed colonel and Harry are also androids. And his own double shows up. The Doctor then does the sensible thing and jumps out a window. Sarah Jane calls him over to safety. Is the Doctor worried? Hell no. All he has to do is go right back in the building he just left despite the loudspeakers all over the base calling for his arrest or death or something.
As it is, he’s not wrong. It is the last place anyone would look.
As for Sarah Jane, she opts to check the rocket for Harry.
Now, yes, we do see the Doctor get into a fight with his double. It’s not a bad fight scene for Doctor Who. Two things complicate. The first is Crayford wondering what the hell’s going on since the Kraal promised no one would die. He’s then shocked to learn the Kraal didn’t do anything for him. Heck, he still has both eyes.
If the Tick were here, he’d use that as proof Crayford is not a secret agent.
And the second thing is the Doctor manages to turn on the radar and shut down all the androids.
OK, so, that should be the end of the invasion. Yeah, the Kraal asshole has a supervirus he’s about to unleash on Sarah Jane, Harry, and the colonel, but Crayford starts to stop him. Crayford dies. Then the Doctor shows up, knocks the Kraal into his own virus, and…also dies when the Kraal shoots him.
OK, it turned out the Doctor reprogrammed his double and sent him in again.
So, the day is saved. Again. Sarah Jane, she wants to go home in a taxi, but the Doctor offers to take her in the TARDIS. She accepts, but somehow, I doubt they’ll be getting her home anytime soon…