The story of how police repeatedly allowed a serial murderer to slip through their fingers.Stephen Port date-raped and murdered four young gay men in East London within fifteen months and dumped all four bodies within a few hundred metres of each other.Yet Barking and Dagenham police failed to link the deaths, until weeks after the fourth one. The film tells the story through eyes of the families of Port's victims, unpicking how the police failed to properly investigate each of the deaths in turn. The police's assumptions that these young gay men had died from self-inflicted overdoses of chem-sex drugs allowed Port to continue raping and killing innocent young men.The film unravels Port's sinister character and modus operandi. Port was motivated by a desire to satisfy his lust for abusive drug fuelled sexual encounters. He found all his victims through gay dating and social media sites, using multiple online profiles.Barking and Dagenham police's failings have led to huge anger amongst the families of Port's victims. Some have accused the police of institutional homophobia, and asked if officers would have investigated more thoroughly, had four young women turned up dead within such a small radius.The Met police have referred themselves to the Independent Police Complaints Commission over their handling of the case and will not comment on specific allegations until the IPCC investigation is complete.