In order to deal with the constant bustle of Hong Kong, director Paul McGuigan and the crew decided to shoot the film "guerilla-style", with the cameras hidden in vans, filming through small holes, and the actors doing their scenes in one take on the streets.
The different type of abilities in the film are: - Movers (move objects with their minds.) - Pushers (control other peoples' thoughts.) - Watchers (see the future.) - Bleeders (emit high-pitched screams that can burst blood vessels.) - Sniffs (track people and objects.) - Shifters (temporarily change what an object looks like to others.) - Wipers (wipe memories.) - Shadows (cloak themselves and others around them from detection.) - Stitchers (heal or unheal people).
Director Paul McGuigan tried to limit the use of digital effects as much as possible, recalling the great directors who didn't have such means available to them yet made up for them with their imagination. In fact the only scenes in which green screens were used were the car chases, as Hong Kong traffic is very heavy.
The idea of a government agency controlling people with special abilities for military and/or intelligence uses is in fact inspired by real-life experiments of the US government, particularly the long-running Stargate Project.
In Greek mythology, Cassandra was given the gift of prophecy, but also cursed so that no one would ever believe her. In this movie, Cassie is able to see the future but has a hard time convincing those around her.