In 2011, the disappearance of Sian O'Callaghan sparked a massive manhunt. When taxi driver Christopher Halliwell confessed and led police to her body, it was only the chilling beginning. This episode of "World's Most Evil Killers" delves into the depths of Halliwell's depravity, revealing a string of murders far beyond Sian's tragic fate. Prepare to be shocked as we uncover the dark secrets hidden behind the seemingly ordinary life of a killer. Subscribe for more true crime stories: youtube.com/c/RealCrime