Stack walked into the room and stared at Adams – it felt as if anything could happen
Austin Stack stepped into the small boardroom of the Davenport Hotel unnoticed by almost everybody.
There had been a stream of late arrivals for the 10.30am press conference on Brexit, so nobody blinked an eyelid when the door quietly opened again.
Those just inside, including Sinn Féin TD Martin Kenny, shuffled to either side to make room for the latest entrant.
With folded arms, Mr Stack stood four feet from Gerry Adams, staring intensely at the Sinn Féin leader. For a second it felt as if anything could happen.
Moments earlier Mr Adams had told reporters that "the murder" of Austin Stack's father Brian was "wrong".
"I have every sympathy with his family and I understand their angst," he said.
After all, Mr Adams reminded us, he had come from a community that suffered as a result of violence. But his knowledge of that violence wasn't up for discussion.
He acknowledged that the flurry of questions from journalists was "legitimate", but he wasn't up for giving any answers.
He had set out his position "in a very detailed and comprehensive way" the night before in the Dáil.
Did he give the name of the IRA leader that met the Stack brothers in 2013 to gardaí? If he hadn't, was he going to? And if he hadn't, why not?
Mr Adams said he had already revealed "in great detail how I attempted to help the Stack family".
He had given the "context and details" of his "endeavours".
"I'm not at this point going to make any further comment," he said.
The meeting was being timidly chaired by TD Kathleen Funchion, who wanted to keep everybody on topic - but she never stood a chance.
The questions kept coming, but the tone in the voices of the reporters was becoming increasingly frustrated.
Was Mr Adams suggesting that naming the IRA leader would put the peace process at risk? How friendly is the Sinn Féin leader with the man?
He talked his way around the houses. "I'm not going to go beyond what I said at this time," he repeated.
It was Mr Adams who signalled the arrival of Mr Stack into the room.
"I want to welcome Austin Stack," lied Gerry Adams, deciding it was better to acknowledge the unwanted guest than try to ignore him.
Everything paused. Ms Funchion looked as if she'd seen a ghost of Sinn Féin past. Then pulses started to race as the cameramen sprang, widening their lenses to capture both men.
Stack took a deep breath. So did everybody else. And then he began: "Gerry Adams, you have information that is crucial to the investigation of my father's murder.
"Gerry Adams, you took myself and my brother Oliver in a blacked-out van to meet with a senior IRA figure, a man you said you trusted. Gerry Adams, I want you to give that information to An Garda Síochána."
The Sinn Féin leader was uncomfortable. The previous evening he didn't even flinch when Alan Farrell named Dessie Ellis and Martin Ferris in the Dáil. Now he was shifting in his seat.
"You, as a public representative, are an absolute disgrace if you don't do that, Gerry Adams," Mr Stack charged.
Adams offered up a timid "right", briefly lifting his arm as if to reassure the room that there would be no hostility from his side.
Mr Stack stalled the interruption by extending his hand in a motion that said 'stop!' "I have no more interest in hearing anything you have to say. You told your lies and untruths in Dáil Éireann yesterday.
'I am now putting firmly the ball in your court. Take the name of the individual that you know to An Garda Síochána."
And with that he was gone back out the door.
Ms Funchion tried to regain control, pointing to the back of the room for the next question, but now the boss wanted to talk.
He cut her off. "Sorry, sorry, let me finish."
"I just want to reject absolutely Austin's assertion that I have told lies or untruths. I haven't. I'm quite content to cooperate with the guards."
The other Gerry Adams emerged. From coy to candid in a matter of minutes. It turned out he hadn't said everything he wanted in his personal statement to Dáil.
"When the two brothers were brought to meet this person, it was by arrangement with them.
"They knew beforehand that what they were going to get was whatever response there was to their justifiable demand for acknowledgement of 'was the IRA involved in their father's killing'. "They didn't have to go. It was their desire to that and the rest of is part of the ongoing controversy," he vented.
He turned to Fianna Fáil leader Micheál Martin, who he accused of seizing on the controversy, while Fine Gael was standing by a man who abused Dáil privilege.
"I didn't spark this course of events. The way this issue was seized upon to make mischief by the leader of Fianna Fáil particularly."
Mr Adams was asked how relations were with Mr Ellis and Mr Ferris, given their furious responses to being named in the Dáil.
Are they as angry with Mr Adams as they are with Alan Farrell?
"I enjoy a good working relationship and a good cordial relationship with all of the Sinn Féin team including Dessie and Martin," he offered.
In any event, he hasn't actually spoken with the bomb-maker or the gun runner since their names were lifted from an email he wrote and placed on the Dáil record.