A film that redefined modern horror and spawned one of the longest-running franchises in the genre has landed on ITVX - and fans are calling it a "masterpiece".

James Wan's 2004 thriller Saw shocked audiences when it first premiered at the Sundance Film Festival, before becoming a worldwide box office sensation. Two decades later, it continues to be hailed as one of the greatest horror films ever made, with viewers still praising its shocking twists, tense atmosphere and groundbreaking low-budget production.

Directed by Wan in his feature debut and written by Leigh Whannell, the film tells the story of two men (Whannell and Cary Elwes) who wake up chained in a grimy, abandoned bathroom. A mysterious tape reveals their horrifying task: one must kill the other to save his own family. As they try to piece together who has trapped them, a sinister figure known as Jigsaw looms in the background, testing their will to survive through deadly "games".

The narrative unfolds in a nonlinear structure, gradually revealing the Jigsaw Killer's methods and motivations. Alongside Whannell and Elwes, the cast includes Danny Glover, Monica Potter, Michael Emerson and Ken Leung.

The origins of Saw are almost as gripping as the film itself. Whannell and Wan originally wrote the script in 2001 in Australia, but struggled to secure funding. They then produced a short film based on a single scene to attract investors.