On the surface this seems like a pretty solid sci-fi movie with spectacular visuals and enough unexpected plot twists to keep the audience guessing. The problem is that it wants us to make the effort to unravel what's really going on, which isn't a bad thing in and of itself, but the film doles out the clues painfully slowly and as soon as you start really examining the story you realize how ridiculous the plot is. Both the backstory as presented at the beginning of the movie and what turns out to be the real story in the end are full of huge holes.
In the opening narration, we're told that in 2017 the Earth is attacked by an alien race called the Scavs. The Scavs have used up all the resources on their planet, so they've come to steal ours. They knock out much of humanity's infrastructure by smashing the moon, which somehow causes earthquakes and tidal waves that ruin our big cities. We fight back using nuclear weapons and eventually defeat the Scavs, but turn what's left of the Earth into a radioactive wasteland in the process.
So the human survivors build a giant spaceship named the Tet (after its tetrahedron shape) and emigrate to Saturn's moon Titan. Now they're the ones who need to strip Earth's remaining resources, so they build giant ocean harvesting machines to gather energy and water. It turns out there are still some Scavs on Earth, and they keep trying to sabotage the harvesters, so artificially intelligent and highly weaponized drones are put in place to protect them. The Scavs sometimes manage to shoot down the drones, so a two-person team is put in place to find and repair the drones. They live in a mostly glass house situated seemingly miles in the air on giant stilt legs.
Tom Cruise plays the action half of the duo, a soldier named Jack who swoops down to the planet on what looks like a jet powered helicopter in order to find and repair the drones. Meanwhile his partner and slightly creepy romantic interest Victoria directs his actions from a high-tech surveillance system in the glass house and reports back to Sally at the Tet, who is a stilted and oddly hesitant woman that Victoria only ever interacts with via video screen.
The first twist of the movie is that both Jack and Victoria have had their memories erased. Neither one really questions why, but Jack occasionally has dreams that he used to live in pre-war New York City and was in love with a Russian woman.
OK, that's the relatively spoiler-free part of the review. BEWARE, BELOW THAR BE SPOILERS. SERIOUSLY, DON'T READ ANY FURTHER IF YOU PLAN TO SEE THE MOVIE. Just jump down to the Conclusion.
Eventually the woman from Jack's dreams, who is named Julia, literally falls to Earth in a hibernation capsule. He saves her from a drone attack, and the two of them end up being contacted by the Scavs, who turn out to be human survivors of the war, not aliens.
Through an unnecessarily complicated series of events, Jack finds out that Julia was his wife before his memory was erased. The two of them, along with Victoria and others were astronauts sent into space to investigate the Tet ship, which is actually an artificially intelligent craft that the aliens sent out into the universe to seek resources. It captured Jack and Victoria and made a clone army out of them, first using them to wipe out the human race and then using them as maintenance workers to keep the Earth harvesters operating. They are given strict instructions not to enter "radiation zones", which in reality are places where other clones are working, because meeting their own clone would ruin the Tet's clever backstory.
The Scavs have a plan to send one of the drones back up to the Tet, armed with a nuclear bomb. They need Jack's cooperation because he's the only human that the drone will obey, since he works for the Tet. In the end the drone gets damaged and can't fly, so Jack volunteers to fly the bomb up to the Tet himself. He's been ordered to bring Julia to the Tet (presumably so it can start cloning her to add to its army), but instead he hides the leader of the Scavs (Morgan Freeman) and the bomb in Julia's hibernation pod, enters the Tet - which lets him in to its innermost chamber despite knowing that he's up to something - and destroys it, killing himself in the process. But all's well that ends well because Julia is carrying his child and eventually meets another Jack clone and lives happily ever after.
Soooo...where to begin? Let's take the opening backstory at face value first. If everything is as Jack and Victoria think it is, then why would their memories need to be erased, and why aren't they more concerned about that? Jack seems a little curious, but Victoria couldn't care less.
Harvesting the energy and resources to keep the remainder of humanity alive seems like a pretty important task, so why send just two people, one of whom is unarmed and the other only carries a laser rifle and pistol? Shouldn't an entire army be guarding those ocean harvesters? Shouldn't Jack and Victoria be a little better protected from the Scavs? Yet neither one ever questions it.
And where did the technology for the Titan colony, ocean harvesters and giant Tet ship come from? The movie is set just 60 years or so in the future, AFTER A NUCLEAR HOLOCAUST, and yet the technology is centuries ahead of what we have now. Even though it turns out to be alien technology, you'd think either Jack or Victoria would wonder where it came from.
If we really did have the ability to create such technology, wouldn't it be easier to try to survive on Earth instead of moving all of humanity to Titan? In the film, it's obvious that there are areas of Earth that seem largely untouched by the war - Jack even builds a little cabin in the woods in one of them. Why not just move the survivors there? Seems like it'd be a lot easier than moving to Titan. In the movie, Jack even indicates that he'd rather remain on Earth than return to Titan, yet he never questions why everyone else went there.
Are we supposed to think that Victoria was in on the alien plot the whole time because she's secretly been in love with Jack all along and was happy to use the invasion as a way of getting rid of the competition (Julia)? The movie kind of hints around in that direction but never really comes right out and says so.
Why is everyone so secretive? Why do the Scavs wear helmets and costumes that make them look like aliens? Why don't they just try to contact Jack and Victoria directly - the Tet's entire story would have crumbled if Morgan Freeman had just strolled out, introduced himself to Jack and explained what was going on. Why does Julia wait until over half way into the movie to tell Jack that she's his wife - wouldn't any normal person mention that right away? Even though he's working for the Tet, she has no reason to distrust him because she was asleep through the entire war and doesn't know that Jack is a clone created by the Tet. Yet she does seem to know about some things that happened while she was asleep, and accepts the destruction of the entire Earth and near-extinction of mankind without batting an eye.
Moving on to what the real story turned out to be - why couldn't the Tet have just accomplished its goals using drones? There were millions of them up on the mother ship. Seems like that would have been a much easier plan than capturing human astronauts, making thousands of clones of them, wiping their memories, inventing this convoluted backstory and hoping they don't bump into each other or the human survivors on Earth. Speaking of which, why DID it take 60 years for Jack to finally figure this out?
Why didn't the Tet destroy the capsule with the hibernating astronauts as it circled the earth for 60 years? How did Morgan Freeman's group know how to call that capsule back down to earth? They mention some mumbo-jumbo about "GPS signals", but it makes no sense. The Tet seems able to control everything remotely, yet Jack is able to fly his jetcopter around at will, and the Tet appears to have no way of tracking him.
During a fight between Jack and one of his clones, a laser pistol fires in a near-random direction and manages to hit Julia square in the stomach a hundred yards away. The resulting wound looks more like a shotgun blast than a laser hole, but Jack has time to carry her to a cave, fly a jetcopter to the nearest glass house, find miracle medicine, fool another Victoria clone into thinking he's "her" Jack, and fly back to save Julia before she dies, despite the fact that she's bleeding profusely. Sure.
The thing many people seem to dwell on (based on IMDB reviews and comments) is how does breaking the moon into pieces cause city-destroying earthquakes and tidal waves? The physics make no sense.
And the biggest question of all - why did they stick Jaime Lannister in this movie and then give him basically no lines and very little to do other than standing around looking menacing?
There are just so many plot holes in this one that it's difficult to enjoy the movie even with the beautiful visuals. Throw in some so-so acting, a generic sounding score that is sometimes wildly mismatched to the actions on the screen, a weak love story that seemed shoehorned in, and the fact that many of the plot elements and action sequences were lifted from better sci-fi films, and this goes from a must-see movie for sci-fi fans to "catch it if it's on free TV and you've got nothing better to do".
Now, let's list those bits that were ripped off from other movies:
I'm sure there are more, but that's all that's coming to mind at the moment.