This week a joint Four Corners/Fairfax report reveals damning evidence that the investigations of key gangland murders in Victoria were deeply flawed, undermining the criminal justice system in the state. Terry Hodson and Carl Williams were career criminals. Hodson was shot twice in the head by a killer who'd come to his home with no apparent sign of a break-in. Williams was bludgeoned to death while in jail. Two murders - six years apart, both linked by key facts. Each was a police informant; both had made serious allegations of police corruption; both were killed with police acutely aware both men were in danger. Despite the extra-ordinary circumstances of the deaths, it's still not clear who ordered their killing. To this day, no one has been convicted of the murder of Terrence Hodson and his wife Christine. Now three insiders speak to reporter Nick McKenzie, casting new light on the murders. How was former detective Paul Dale linked to the Melbourne underworld? What was his relationship with Carl Williams? And why didn't police, tapping the phones of criminals, alert other police about the information they had gathered and the potentially lethal connections they'd uncovered? This story throws new light on a shocking chapter of Australian criminal history and clearly asks questions about the administration of justice in the past decade and the crucial issue facing all police forces, how to protect key informers in cases involving the criminal underworld and allegations of police corruption.