Man, the Doctor can’t do right by the Silurians.
Of course, in this serial, it doesn’t look like he can do much right by anybody.
Let’s review: a combined force of Sea Devils, Silurians, and a sea monster have taken over Sea Base 4, holding the survivors–including the Doctor, Tegan, and Turlough–hostage. Now, the Silurian leader remembers the Doctor and will even let the Doctor and his companions go once they accomplish their plan…namely to use Sea Base 4 to start a nuclear war, annihilate the human race, and leave the planet safe for his own kind and only his own kind.
This dick is a genocidal dick. That’s among the worst kinds.
Now, the Doctor won’t stand for that, and the Sea Base’s commander is forced to help since his own personnel are among the hostages.
Except, Turlough and one woman are escaping through a vent.
And during a firefight, with the Doctor and Tegan on one side of a store room and Turlough and the woman on the other, a gas canister full of the anti-reptile gas is hit, and the Sea Devil trying to corral the foursome suddenly keels over and dies. Heck, his face turns to ooze. It’s not a good way to go.
So, the Doctor has a way of saving the day. He’s gonna flood the station with the gas, having Tegan and Turlough stand by with oxygen masks to keep the downed Silurians and Sea Devils alive because the Doctor hates killing things unnecessarily.
That mostly works, but not before a missile is launched. Since the missiles are not controlled mentally, the Doctor takes control there while the wounded Base commander does everything else, and there isn’t going to be a nuclear war to wipe out the human race.
Of course, most everyone else, human or reptile, died anyway with Turlough shooting the Silurian leader before he could bring down the Doctor. So, really, no nuclear war, but still a lot of death.
Because, you know, it never works out when the Doctor encounters the Silurians. Those lizards should just go back to sleep as soon as they find out the Doctor is wandering around somewhere. It’s safer.