Like all game changers within the horror genre, SAW was an independent success, a low-budget champion that flourished without the patronage of a big studio. Not bad for the most successful horror franchise ever, which has spawned subsidiary media and masses of merchandise, including a theme park rollercoaster ride. What is it about SAW that attracted such a following? In his contribution to the "Devil's Advocates" series, Ben Poole considers the SAW...