MELBOURNE police believe the killer of Hongkong-Australian schoolgirl Karmein Chan may have inside knowledge of police plans. Two years after Karmein was abducted and murdered, Victorian police are trying to revive hopes in worried Melbourne parents that the man - dubbed Mr Cruel - will be caught. Assistant Commissioner (Crime) Mr Neil O'Loughlin said yesterday: ''We are sure the net is tightening around the man responsible.'' John and Phyllis Chan, Karmein's restaurateur parents, emigrated from Hongkong 16 years ago. They want to return to the territory or start a new life in the US but are trapped in Australia because of their failure to sell their business and home. Karmein's abduction and murder - her body was found in a shallow grave on April 9 last year - has turned many Melbourne homes into fortresses as parents fear for their children. A safe neighbourhood is now cited by real estate agents as a major concern of Hongkong home-buyers. And as police assure worried parents the A$3 million (HK$16.4 million) manhunt is not over, despite reports they are considering scaling down the Spectrum task force set up to find Mr Cruel, it has been revealed that he may have had inside knowledge. Karmein's abduction at knifepoint from her luxury suburban home on April 13, 1991, came the day after Operation Challenge, set up to investigate two earlier kidnappings by Mr Cruel, was being scaled down. And eight months later, while task force detectives and their partners enjoyed a rare social evening together, there was another attempted abduction. Mr Cruel has not been ruled out as the perpetrator of that attempt. A police spokesman told the South China Morning Post there was no evidence to suggest Mr Cruel was a police officer. Whether he had inside information that led to those odd coincidences was not known. The Spectrum task force still has 35 staff working on what has become Victoria's biggest manhunt. Earlier this year, in what was seen as a last-ditch effort to find the killer, police revealed details of a bedroom in which the two victims he freed, Sharon Wills and Nicola Lynas, told police they had been held. Police checked 30,000 homes under or near flight paths because the girls had heard jets overhead. That revelation brought thousands of tip-offs. Task force detectives believe it is highly likely someone is protecting Mr Cruel. Convicted American child kidnapper and killer Richard Sterrett this week agreed to help police. His own exploits - several abductions before he shot dead a young girl - uncannily resemble Mr Cruel's. He was interviewed by police at his South Carolina hospital for the criminally insane. Sterrett said: ''If there is a small chance that I can help them I am prepared to try.'' Detectives have worked 20,000 hours of unpaid overtime, travelled almost 720,000 kilometres, have the largest computer database ever assembled in a police investigation in Australia and have processed 9,600 public tip-offs. They have developed a detailed psychological profile of Mr Cruel as outwardly an ordinary man.