Vira saves the Doctor by turning up and shooting Noah, but he is only stunned for a moment. He tells Vira that the Wirrn are going to nom all the mannys because some other mannys nomed all the Wirrn in Andromeda (greedy mannys). Another Wirrn hatches and the Doctor and Vira run away so they don't get nomed.
The Doctor comes up with a plan to electric the Wirrn and everybody starts to help with it. Harry, Vira and Rogin go to a shuttle which they can use for electrics since the Wirrn have stolen all the electrics in the Ark. At least I think that's what is happening. One thing I am sure of is that they are still in peril because the Wirrn are sneaking about looking scary.
Sarah has to crawl through a small triangle as her part of the Doctor's plan. She gets stuck until the Doctor trolls her into being unstuck and going again.
"What?! Conned again..! You're a brute."
"Me a brute? Don't be ungrateful. I was only encouraging you."
The Doctor turns on the electric just in time to zap a Wirrn. Another Wirrn tentacles Sarah's legs and then the Doctor's legs until the Doctor zaps it as well.
Noah says "Your resistance is useless. We control the Ark." He tries to persuade the Doctor and Vira to give up. Noah says he will turn off the air unless the awake mannys all go away and leave the sleeping mannys to be Wirrn noms.
The Doctor counters by appealing to Noah as a manny not as a Wirrn, telling him to go away and leave Earth for the mannys (and the cats, I hope). Noah's reply is a rejection, but hesitantly delivered:
"I have no memory of the Earth."
Is this a lie? We have already found out that the Wirrn should have all of Noah's memories. What does it mean?
The Wirrn attack the shuttle and there are lots of them, like horrible Flying Things. The Doctor tells Harry, Vira and Rogin to leave the shuttle so only Wirrn are on it. Then he goes to launch the shuttle away from the Ark, but Rogin punches him out and does it instead - which means he is the one who gets blasted by steam instead of the Doctor.
Noah telephones Vira from the shuttle to say "Goodbye Vira..." and then the shuttle blows up with all the Wirrn on board. Noah has fooled the Wirrn into all getting blown up and so he has defeated them in the end and saved all the other mannys.
Vira wants to teleport down to Earth, but the Doctor has to fix the teleport first. Sarah does a very quick costume change to be ready for the next story.
The Ark in Space is a great story, even though there are no cats in it. The Wirrn are a scary monster (which helped keep Cthulhu happy, or as happy as a grumpy Great Old One ever gets) and the story is always exciting. The story is also cleverly done in that there are only a minimal number of characters, each of whom has their own important part to play. Sadly that meant that there was no place for any cats to be in it.