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. 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.