While in film school, Whannell met James Wan. Together, the two wrote a script for what would become "Saw". After making a short film in 2003 to showcase the intensity of the "Saw" script, the feature film version, directed by Wan, was made in 2004 and became a low-budget sleeper hit. Whannell played Adam Stanheight in the film, one of the main characters. The popularity of "Saw" led to a sequel, "Saw II", which was directed and co-written by Darren Lynn Bousman, and on which Whannell co-wrote and revised Bousman's original script, titled "The Desperate". Whannell also served as an executive producer.