Grieving father Frederick Parkin will fly out to Australia in a quest to find the truth about his son's mysterious death.
Mr Parkin on Friday claimed his "gentleman" son would never dabble in drugs and the evidence pointed to robbery and murder.
Computer analyst Stephen, 27, was found dead in a seedy hotel room in Sydney last December, following an apparent drugs overdose. A combination of opium and alcohol was found in his blood.
A coroner recorded an open verdict at Stephen's inquest on Thursday after hearing how needle wounds were found on his right arm. Stephen was right-handed.
About £250 was also missing from his wallet while a mysterious third man was spotted talking to Stephen on the plane to Australia.
Speaking from his home in Ferry Road, Hullbridge, Mr Parkin said he had received more information about his son's death and would liaise with police in Australia.
He said: "I believe a third person was involved in my son's death. Needle wounds were found in his right arm but my son was right-handed. No syringe was found in the room - and his money was missing.
"There was talk about him talking to someone on a plane but I do not believe that my son would become involved in some sort of drugs scenario just hours after meeting someone.
"He was not into drugs and neither were his friends. I think the implication is that he was robbed."
He added: "We will talk to the police and according to what they say we may or may not take it further.
"I do not know what will come of it but it's the closest we've got to finding the truth."
Stephen was a self-made man who had a "bright present and a bright future", according to his father and mother Valerie.
He went to Sweyne School, Rayleigh, and then Seevic in Benfleet before striking out alone with his own computer company Rum Ranch.
While his firm developed, he worked in Brighton for the credit card company American Express.
He was a well known sportsman, fighting as an amateur boxer for clubs on Canvey and Rayleigh and became a schoolboy champion when he was 14.
He had planned to buy a house in Brighton when he returned from Australia.
Converted for the new archive on 19 November 2001. Some images and formatting may have been lost in the conversion.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article