The first rule of the game is trust no-one. When teen reality star Anton Frazer unveils his latest stunt - a live- streamed, citywide game of Tag in which the prize is to be one of his live-in acolytes - his fans go wild. The whole world is watching. The contestants are kitted out with body cams, GPS trackers and pressure sensors that, if activated by a competitor, will send them out of the running. They venture into night-time London to hunt each other down. Four contestants in particular have alternative motives for being there, secret reasons to want to win despite the risk: money, revenge,