Let's get this straight: "Based on true events," here means that someone came to Bryan Bertino's house and asked for someone who wasn't there, and he later discovered empty houses in the neighbourhood were burgled. Actually, when we lived in Tulse Hill, something very similar happened: two very suspicious characters knocked on the door one afternoon, and were clearly not expecting anyone to be in. We'd had a break-in attempt not long before, the week after my housemate had bought a new TV set in Brixton, and suspect someone in the store was passing the info on, for a spot of impromptu repossession. This has nothing to do with the movie, but there's so little plot here, I feel the need to pad out the paragraph usually devoted to such things. Basically, it takes place over one night at a remote holiday house inhabited by Kristen (Tyler) and James (Speedman), which falls under siege by three people wearing masks, who break in and hunt the two residents down.
The early stages are mostly tapping into a very raw, basic fear - home invasion - and is very effective when it does so, most notably when Kristen is alone, and hearing noises outside the house, along with a relentless banging at the door. This is almost insanely creepy: our house is not exactly the middle of nowhere, and we still found ourselves listening nervously for sounds outside. Once the intruders...well, intrude, and begin interacting with Kristen and James, things become somewhat less effective, mostly because some of the choices made by them are not the ones we would have made. There is too much horror-movie cliché, such as the heroine hiding in a closet with a slatted door. There are some effective moments - when Kirsten demands to know why the assailants are doing this, the answer is simple: "Because you were home." However, nothing quite matches the chills created earlier on and the film peters out rather than building on what had been an excellent foundation.