It was nearly two years ago that Sydney man Paul Sekeres, a married father of two, walked out of his Kingsgrove home and vanished.
As the anniversary of his disappearance approaches, police say they believe a number of people may know what happened to the self-employed concreter, but are afraid or unwilling to come forward.
Detectives have no idea if Mr Sekeres, who was 38 when he disappeared, is alive or dead, but they are treating his disappearance as suspicious.
"We can't find any signs that he is continuing his life as he would have normally, which gives us some concerns," Detective Inspector Paul Simpkins, from St George police, said.
"We're unsure of his background and that's why we're seeking information from any friends or acquaintances that may be able to shed some light on his activities away from his family."
What police do know is that Mr Sekeres was last seen at his home in Kingsgrove, in Sydney's south, on January 30, 2012.
His car was found a short time later in Narellan and police believe he may have driven to the area.
The reason for that visit is unclear.
"We have no real information as to why he was in that area at the time," Inspector Simpkins said.
"He did work for himself for a period of time, but there has been no further activity in relation to his business. We're not sure what he was doing."
Inspector Simpkins said police launched an investigation into Mr Sekeres' disappearance at the time and had been in contact with his family.
"They're obviously concerned because he's been missing for such an extended period of time and have been assisting us in trying to locate him."
Mr Sekeres is not believed to suffer depression or any diagnosed mental illness, but little is known about his life away from his family, Inspector Simpkins said.
"His background or his activities away from the family are unknown, so we are trying to establish that information.
“We have received some useful information from the community to date. However, we do believe there are a number of people out there who can provide us with more information, the type of information that will help us determine exactly what has happened to Mr Sekeres.
“If you know where he is, or what has happened to him, please get in touch with us.
“We don't need to know who you are, all we need is the information you have to hand. You can contact Crime Stoppers anonymously and your call will be treated in the strictest of confidence.”
Police have urged anyone with information to contact Crime Stoppers on 1800 333 000 or use the Crime Stoppers online reporting page.