Danny Boyle gave the South by Southwest (SXSW) festival a sneak preview of his new movie Saturday, a dark thriller in which the director says you won\'t know the good guy until the end of the story. \"Trance,\" which opens March 27 in Europe and next month in North America, stars James McAvoy, Rosario Dawson and Vincent Cassel in a tale that blends the world of fine art with criminal gangs and hypnotherapy. In conversation with New York Times writer David Carr, the Oscar-winning director of \"Slumdog Millionaire\" said he recently noticed a common thread in his genre-jumping projects -- a character with incredible odds to overcome. \"The difference in this film is that you don\'t know which character it is,\" he said. \"You don\'t know until the end.\" Besides the trailer already up for viewing online, Boyle presented a harrowing segment, set at night on harbor docks, in which Cassel is trapped inside a car that McAvoy soaks with gasoline and then sets on fire. Boyle, 56, affably dismissed suggestions he was spoiling the plot for the SXSW crowd, noting that \"Trance\" -- befitting of its title -- opens with \"an amnesia effect\" that should work on filmgoers. \"At first you\'re absolutely certain you should root for James McAvoy,\" said Boyle, whose other crowd-pleasing efforts include \"Trainspotting, \"127 Hours\" and the opening ceremony of the 2012 London Olympic Games. \"But then it kind of shifts... and that\'s one of the appeals of the film.\" Speaking to an audience filled with independent filmmakers with dreams of Hollywood success, Boyle said he has been blessed to work with major studios that give him a \"cap\" -- a spending limit -- but trust him with full creative control. Joining Boyle on stage at SXSW was Rick Smith, his longtime soundtrack collaborator since \"Trainspotting\" in 1996, which prominently featured music from Smith\'s electronic dance music group Underworld. Smith noted that Underworld was reluctant at first to contribute to \"Trainspotting\" after Boyle told him it was about a group of heroin addicts in a grim corner of Scotland\'s otherwise picturesque capital Edinburgh. \"Then Danny said, \'Come along and I\'ll show you 15 minutes,\'\" Smith recalled. He then viewed a scene in which Ewan McGregor dives into a sordid toilet bowl then swims through tropical waters to recover some lost suppositories. That same clip was screened at Saturday\'s discussion -- along with a segment from Boyle\'s 1994 directorial film debut \"Shallow Grave\" -- and Smith said he immediately saw humor, intelligence and compassion in the project. \"And at the end of the clip, it became the complete opposite: \'You can use anything of ours that you want in your film,\'\" the musician remembered telling Boyle. Boyle, who grew up with late 1970s punk and then frequented raves in the 1990s, cited music as a powerful influence. \"I see my life in pop music... and you tell your stories through that prism,\" he said.