In 2008, BBC cameras filmed two Swedish sisters throwing themselves into traffic on the M6. When it was shown on BBC One, nearly 7 million viewers were glued to their screens, and millions more watched it later on YouTube.The twins met in Ireland before traveling to England. After their odd behavior caused them to be left at an M6 service station, they ran on to the motorway numerous times and were struck by oncoming vehicles, causing Ursula to be incapacitated. Sabina refused medical aid and attacked a police officer, at which point she was arrested.The footage was shocking. One previewer wrote On no account miss this documentary. It opens with what is perhaps the most extraordinary footage I've seen on TV.But this amazing footage was only part of an even more incredible story, one which could not be told at the time for legal reasons.Two years later, this documentary reveals the full story of the hours just before the cameras captured that motorway footage, and the even more chilling story of what happened over next 72 hours, which left one of the sisters fleeing the scene of a crime, after she had stabbed a man through the chest.