The story was influenced by a short film Joshua David Hall made the year before, called 'Separation', which was about a teenager (played by Ben Arnold) who kidnaps a bully (played by Eric Bay-Andersen) and takes him to the woods to kill him. Ironically, in this film the roles are reversed - here, Eric Bay-Andersen plays the kidnapper and Ben Arnold plays the victim. The short can be found on YouTube.
The film-makers mainly worked from an outline. The only scenes that were fully scripted were the scene in the bar where Dan and Matt first discuss their plan and the scenes in Brighton. Other scenes, like the one where they torture Shane, were completely improvised.
In the scene where Dan and Matt pull into the garage area, Michael Roberts thought the scene was going to end with Eric Bay-Andersen shutting the car trunk (he was lying underneath the car rather than in the trunk). When Eric turned the engine on and reversed out, Michael got a face full of smoke from the exhaust pipe and had to roll out of the way quickly to avoid being run over.
In the scene where Dan is driving, Joshua David Hall is not actually driving. He didn't have a driver's license at the time, and so the shot was achieved by having Joshua sit in the passenger seat with his arm held up and the shot was flipped in post-production.
Dan's (Joshua David Hall's) parents in the birthday scene were actually played by Eric Bay-Andersen's (Matt's) parents. To avoid audiences noticing that Matt looked a lot more like Dan's parents than Dan did, the film-makers decided not to have them in the same shot.
The trivia items below may give away important plot points.
This films shares many similarities with Memento (2000): both are told in non-linear fashion, both deal with men seeking revenge for the rape of a loved one, both open with a murder which takes place at the end of the story (in which the protagonist kills a friend of his), and both end with the protagonist driving away from a murder scene (in car that belongs to someone else) wondering if he's done the right thing.
Made by the same cast and crew as Take (2008). Joshua David Hall actually had the initial idea for the story back in 2007, but it wasn't until they made 'Take' that the film-makers felt ready to tackle the darker subject matter the story required. There are several differences between the original idea and the final film - originally, the bet between Dan and Matt was that Dan could kill three people in one hour (one of them being an abusive stepfather). Dan's sister was also meant to be 13 rather than 18, but the film-makers didn't want to force an actress that young to act in a rape scene. And the ending originally involved Dan killing Matt by crushing his head in a car door, and then burying him.
Other similarities with Take (2008): both were filmed in Weybridge in Surrey, the same house and car were used in both films, and Joshua David Hall's character in both films takes a gun out of a backpack he's been carrying the whole time.