Read more about [REC] in our Disaster Movie Database!
Foreword: [REC] is a fun little time-passer in the found footage genre (and, to some extent, the rage-infected pseudo-zombie genre), with some genuinely creepy (but, for those of us who love extreme horror, not terrifying) moments. The only thing that drove me nuts (no, not the subtitles; I don't mind subtitles at all) was protagonist Angela Vidal. Manuela Velasco, who plays Angela, is quite good as the pretty blonde airhead type who typically hosts third-rate reality/entertainment shows (I guess TV is just as crappy in Spain as it is in the U.S.); it's the character who'll make you want to turn into a rage-infected zombie yourself just so you can put an end to her shrill, incessant screaming.
[REC] was remade in the U.S. just a year later as Quarantine. If you've seen Quarantine, you've seen [REC], and vice versa. if you have to make a choice, I'd urge you to choose [REC] over Quarantine, but if you're too lazy to read subtitles, then Quarantine is the one you want. You won't suffer if you watch either and not the other; neither movie is Citizen Kane.
However, [REC] just works better as a found-footage film, in part because the locations are (reportedly) real, while Quarantine feels like it was shot on a set, but mostly because [REC] uses actors unknown to a wide U.S. audience. It's pretty difficult to suspend one's disbelief for a found-footage movie when you recognize half the actors from long-running TV roles (e.g., Jennifer Carpenter from "Dexter," Steve Harris from "The Practice," et al.).
Now for the spoiler:
Too-perky and annoying TV reporter Angela Vidal (Manuela Velasco) and her cameraman Pablo (Pablo Rosso) are spending the night with a local fire station crew for a show called "While You're Asleep." Just when you (and the audience for "While You're Asleep") are about to nod off (or tune out) after deciding nothing ever happens in Barcelona, the crew gets a call to rescue an old woman trapped in her apartment.
With Angela and Pablo in tow, the firefighters arrive as the cops are breaking down the woman's door. The woman is found acting, well, rabid, and bites a cop and a firefighter. The landlord tries to shoo Angela and Pablo out of the apartment (he seems worried about bad publicity), but it's a pretty pointless move, as our intrepid crap-TV crew aren't getting out anyway (and neither is anybody else).
The building, you see, has been quarantined. A dog belonging to a little girl living in the building was infected with some sort of virus, and when taken to the vet's office went nuts and killed some other animals. The dog was put down, but the little girl was infected, and is now exhibiting signs of some sort of zombie fever. (Her mother keeps insisting the girl's less-than-socially-acceptable behavior is the result of nothing more serious than tonsillitis. Joke's on Mommy when Precious takes a chomp of her flesh!) Now the virus is spreading to the rest of the residents.
The firefighters didn't know any of this when they arrived; they just happened to show up at the worst possible moment. Now they and Angela and Pablo and everyone else are trapped inside (and the authorities outside obviously don't care; they turn a deaf ear to screams for help).
After battling apartment dwellers who would fit right in with the rage-infected killers of 28 Days Later, Anegla and Pablo fight their way to the building manager's apartment to retrieve the key to a portal into the sewer system, through which they hope to escape. They find the key, but are trapped upstairs by infected residents still running around loose on the floors below.
Angela and Pablo flee to the building's penthouse, where they discover that its owner was researching a virus the Vatican believed was the real cause of demonic possession (no, we couldn't make this up), and was testing it on a "possessed" girl he was keeping in the penthouse. When he found he couldn't cure her (I guess he didn't want to kill her), he sealed her into the attic of the building to let her die of starvation (which is ever so much more humane than just killing her, isn't it?).
None too wisely, Angela and Pablo decide to check out the attic, where they're greeted by a scary little boy (where the heck did he come from?!) who attacks Pablo and breaks the light on his camera. Pablo turns on the camera's night vision and discovers Patient Zero, emaciated to death-camp level, but not incapacitated; she attacks Pablo, who drops the camera. (Pablo, it's safe to assume, is killed.)
Angela (who can't see in the dark, remember), finds the camera and picks it up, but does the usual Horror-Damsel-in-Distress thing and trips and drops it. As she struggles to find it again, the camera, just inches in front of her outstretched hands, continues to roll. Suddenly, something grabs Angela by the legs and drags her, screaming, off into the dark.
[REC]2 (2009) We need a spoiler!
[REC] Apocalypse (2012) We need a spoiler!
[REC]3 Genesis (2012) We need a spoiler!