Very spoilery about the Moonfall ending. (If you’re looking for my review, it’s here.)
What is the Moon?
The Moon is hollow, an ancient megastructure built as an ark by a long-dead alien race. They had achieved societal perfection, until billions of years ago their AI turned on them in the form of black swarms. The aliens built a series of arks which were sent off to far corners of the universe to seed humanity, each ark powered by a white dwarf star at its centre. The black swarms hunted them down though, with our Moon the only ark to escape. The aliens were long gone but their last actions were to ensure the founding of the human race, on Earth.
The black swarm finally discovered the Moon and breached its external defences, emerging from a hole in the lunar surface in 2011 to attack astronaut Brian Harper and his crew in space. It later becomes apparent that the swarm looks for a combination of technology and organic matter, which of course includes modern humans, especially astronauts in their space shuttles.

How long has it been known?
The elderly Holdenfield (Donald Sutherland), who now works in a basement at NASA, finds Jo there as she is tracking down the webcam footage from Brian’s helmet taken during the 2011 disaster. She finally sees what Brian saw, and realises NASA knew the truth of what had happened. Holdenfield tells her that the reason contact was lost with the Apollo 11 Moon landing was actually deliberate, to stop ordinary people seeing what the astronauts had discovered: that the Moon was not what we think it is.
Why is the Moon on the move?
The Moon is now falling out of orbit because the black swarm, which has got inside the Moon, has destabilised its core by feeding off the white dwarf’s energy.
What happens?
The US fact-finding mission to the Moon — established after they discover its orbit has changed — ends in catastrophic failure, with the swarm finding and killing the three astronauts on board. Thanks to space exploration budget cuts, the only way to go back is to get one of the space shuttles out of its museum home, taking with them an EMP bomb that had been in development before cuts had forced the programme’s closure.
As the Moon heads towards Earth, people are trying to get to higher ground to escape the enormous tides caused by its increasing gravitational pull. Jo and Brian are at the final NASA launch site with a crew which is about to blast off. The aim is for them to destroy the swarm with the bomb, which should mean the Moon can right itself back into its orbit. But as the Moon gets closer to Earth, our planet is bombarded with flaming lunar rock and vast tidal waves. One engine on the space shuttle is destroyed. Only Brian has experience flying a space shuttle without engines, so Jo stands down almost everyone on the base, including the original crew, deciding that she, Brian and KC will fly the mission using the Moon’s gravitational pull to get them there.
Brian’s son Sonny, Jo’s young son Jimmy and Jimmy’s caregiver, international exchange student Michelle, set off in a 4X4 for the government bunker in Colorado. Sonny is driving, a distance of several hundred miles. The final helicopter takes off too, but is caught in a giant wave (it’s not clear if the last helicopter makes it. My friend is sure they all died, I am convinced they survive!) The space shuttle has to blast off through the wave, which it manages.
As they get into the snowy mountains, Sonny, Michelle and Jimmy are held up and their truck stolen, along with Jimmy’s bag containing his phone — the phone that has a direct link to his Colonel father Doug who is in the bunker. Now the three of them have no way of getting inside. Sonny takes them to a gated community in Aspen where his mother Brenda, stepfather Tom and two young half-sisters are holed up. As the Moon gets closer, oxygen in the air is sucked up, but Tom remembers a nearby firefighter depot — they all travel there in his Lexus where they collect some masks and bottled oxygen. At the depot they’re attacked by the three who previously stole Sonny’s truck, but he has his own gun and fights them off. A car chase ensues, with Tom’s car outrunning the thugs, who are killed in fiery crashes as the land starts breaking up.
The group stop and mask up, before making for a nearby tunnel in the hillside where they think they can hide out. On the way one of the girls’ oxygen tanks runs out. Tom gives her his, and sends her forward to the others who have reached the tunnel mouth, telling her he will be behind her. He sinks to the snowy ground and dies. When she reaches the tunnel, Sonny goes back for him but is injured and pinned under a tree. Michelle goes to look for him and manages to free him, aided by the changes in gravity. By now the Moon is close to the Earth. They run back to the tunnel, with gravity meaning they are able to leap together over the gap in the destroyed road to the tunnel entrance. The oxygen has now come back and they all hide in the tunnel.
Up in space, Brian, Jo and KC make it into the Moon and marvel at its internal structure, including fields. They hope the swarm, seeking out tech, can be lured to the bomb.

They are pursued by the black swarm and make it into a secure area of the internal structure, though all are left unconscious. Brian wakes and discovers holograms of Sonny as a young boy and now, though he’s told this is the operating system of the Moon speaking through the holograms. The hologram explains why the structure is here and about the past of the ancient aliens. They are the human race’s ancestors, and though they knew they were to be destroyed by their own AI they ensured humanity would go on, with the Earth to be seeded with human DNA.
He’s joined by Jo and KC. Brian now knows they can’t just set their bomb off to lure out the black swarm, as it needs bait: organic matter (a human) plus the tech of the bomb. He is planning on sacrificing himself, but instead KC silently moves into the module at the back of their craft and shuts the window, explaining to Brian what he’s doing. He asks that they tell his elderly mother (who has been evacuated to safety, along with their pet cat) that he was a success.
Back in the bunker, Jo’s ex-husband Doug prevents the military top brass from setting off nuclear weapons aimed at the Moon, which would kill Jo and cloak the Earth in radioactive fallout.
KC’s module is released and the swarm comes for him. He waits until he is inside the AI creature and then explodes the bomb. Jo and Brian head back to Earth, their craft landing in the snowy mountains, right next to the uprooted Chrysler building. With the swarm now gone, the white dwarf star at the Moon’s centre is no longer disrupted and the Moon starts moving back into its correct orbit.
A military helicopter arrives, and Sonny, Jimmy, Michelle, Brenda and her two girls disembark.
Back in the Moon, KC meets a hologram of his own mother and their cat. He’s told it’s the operating system, and that his consciousness has been uploaded into the Moon. He’s also told that they have work to do.
Themes
Parents and children: there’s a parallel between the super-advanced aliens who have been dead for billions of years, setting in place a future for human beings from their last ark, and the relationship between Bryan and his troubled son Sonny, who he tries to help (despite Sonny’s initial anger at his father).
Our vulnerabilities: technology can make us vulnerable if it is not handled appropriately, whether the original GIs merging into swarms to attack their creators, or our love of tech making us vulnerable to the swarms later on.
Hubris: despite the aliens’ work to ensure our survival, they were consumed by their own creation. While they sowed the seeds of their future they also first sowed the seeds of their own destruction.
What doesn’t make sense
I mean more than is usual in epic disaster movies. I mentioned in my review that Jo keeps young Jimmy and Michelle with her for far too long at the base, resulting in them having to drive hundreds of miles with Sonny through an extremely dangerous situation, full of terrified people, to get to the Colorado government bunker. Surely she’d have sent them off earlier in a helicopter? Even if she couldn’t get them on a military or government helicopter wouldn’t she send them off overland much earlier?
Near the end of the film, Bryan states that the swarm didn’t simply attack the Earth in 2011 (and we were a huge mass of organic matter and technology even then!) because it “knew” the Moon was programmed to keep re-seeding the planet, so it was pointless. It’s possible the swarm was deliberately feeding off the white dwarf to make the Moon fall into the Earth and destroy humanity that way, so there could be no re-seeding of Earth by the Moon in future, but that didn’t seem particularly clear.