Caution: potential spoilers.
This is a 2012 remake of the 1990 film of the same name, both of which are based on the 1966 story "We Can Remember It for You Wholesale," by Philip K. Dick. I've never read the story, but I did see the original movie sometime in the early 90s. As for the remake, it really wasn't necessary, and I don't think it was as good as the original. Still, I didn't think it was bad. It's more of an action movie than a sci-fi movie (the original was more sci-fi, I think), and it works well enough in that genre. But... I'm putting my review under "science fiction" just because... there would be no plot without the sci-fi premise. It really should be more mind-bending than it is; you should be asking yourself the whole time, "Is any of this really happening, or what?" And you can still ask yourself that if you want, but it's not really necessary. I'm not going to tell you whether any of it is actually happening, but... honestly, it's not that important.
So, it starts with some text on the screen explaining the world in which the movie is set. I don't know what year it is, but it's sometime in the future. At the end of the 21st century, there was a war that left most of the Earth uninhabitable. (Mars will be mentioned in passing, later on, but unlike the original, this movie is set entirely on Earth.) There are two inhabited regions left on Earth: the United Federation of Britain (UFB) and the Colony (Australia). And there's an elevator ("the Fall") running through the center of the planet, connecting the two places. Once we know this, the action starts: a man (played by Colin Farrell) wakes up in the middle of a battle in a lab or something. He's joined by a woman (Jessica Biel), his partner in... some kind of spy operation, or something. They're being chased by enemies. The guy gets caught, then he wakes up in bed with his wife. His name is Doug Quaid, and his wife is named Lori (Kate Beckinsale). They're residents of the Colony, and there have been terrorist attacks recently, by a group called the Resistance. The leader of the Resistance is a man named Matthias (Bill Nighy), and the leader of the UFB is Cohaagen (Bryan Cranston). Anyway, after the latest attack, Lori gets called away to work. Soon thereafter, Doug and his friend Harry take the Fall to their job at a UFB factory that manufactures robotic soldiers and/or cops called synthetics. Anyway, Doug has recently seen an ad for a business called Rekall, which can give people artificial memories. He thinks this might help both with the trouble he's been having sleeping recently, and with a general sense that his life is boring. But Harry advises against it.
That night, Doug goes to Rekall, where he opts for receiving memories of being a spy. But as soon as he gets prepped for the procedure (seemingly before it actually begins), there seems to be a problem. He's not supposed to get memories of things that are part of his real life, because that could fry his brain. But the guy who's going to give him the false memories (played by John Cho) says his psych scan indicates he's actually a spy. Then the cops bust in, and Doug (who is suddenly a badass) kills them all. He goes home, and Lori at first tells him he must have imagined it because of whatever Rekall did to him, but then she starts trying to kill him (and she is also now a badass). Of course Doug is confused as hell, but it seems Lori is not really his wife (he has no wife), and the life he thinks is his, is something he's only been living for like six weeks, I guess. There is no "Doug Quaid." He has no idea who he really is, and he doesn't even want to be anyone other than the person he remembers being. But now he's on the run from the police and Lori, and he has no idea why. After awhile, he gets rescued by the woman from his dreams, whose name is Melina. There's a hovercar chase, with Doug and Melina fleeing the police. Finally they make it to the home of Doug's "real" self, who turns out to be a spy named Hauser, who originally worked for Cohaagen, but had later joined the Resistance. And then the UFB forces had captured him and implanted the false "Doug" identity, for reasons. Anyway, Doug/Hauser and Melina will continue to be chased by Lori and the police, and ultimately they have to make their way to Matthias's secret base, to deliver a code that would deactivate all the synthetics. Which would thwart Cohaagen's planned invasion of the Colony.
And... more stuff happens. I don't feel like I've actually spoiled anything, but you might disagree. Either way, I'm not revealing any more of the plot. Anyway, there were lots of cool action sequences and cool visual effects and whatnot. The story itself was just okay. I mean, I wouldn't really call it good or bad, but at least I found the movie acceptably entertaining, and not a waste of my two hours. But I also don't think I would have been missing anything if I'd skipped it. And I don't feel the need to ever watch it again, unlike the original.
Oh, right. I also meant to mention one similarity between the films: they both have a scene that includes a woman with three breasts. You know, in case you're into that kind of thing....