Mr Kieran Byrne, who was abducted from his home by armed men posing as gardai, was interrogated and beaten for two days before being released, it emerged yesterday.
While there is no official comment on the affair, gardai believe he was abducted by members of the Provisional IRA.
Mr Byrne (26), from Ballymun, was set free on Saturday night at Blanchardstown.
He had been taken to waste ground and released from a car, which was then burned by his abductors.
He took a taxi to his home in Balcurris Road, where he was reunited with his partner and young son.
He then went to Ballymun Garda station where he was seen by a doctor, and gave an outline of his abduction. He was later taken to the Mater Hospital for treatment for injuries sustained during the beatings.
Mr Byrne and his family declined requests by the media to speak about his ordeal.
His abduction began at 10 p.m. on Thursday when three men called at his house and identified themselves as gardai from the Bridewell station. He was apparently taken in by the ruse and agreed to go with them. He was driven away in a green car.
When his family telephoned the station the next morning there was no sign of him there. Further checks by gardai showed he had not been taken to any Garda station.
A public alert was issued, and Mr Byrne's photograph was circulated to the media by the Garda Press Office.
The senior officer in the North Dublin Division, Chief Supt Jim Murphy, said gardai were very concerned for Mr Byrne's wellbeing.
There was no statement from the IRA or Sinn Fein about the incident.