James McClean fired the Republic of Ireland to the top of Group D with a priceless win in Austria which keeps their hopes of World Cup qualification very much alive.
Here's what we learned at the Ernst Happel Stadium in Vienna.
1. Harry Arter is a genuine international footballer
Bournemouth midfielder Arter has had to wait a long time for his first competitive appearance for Ireland, prompting speculation - fiercely denied after an unwarranted backlash - that he could instead opt to represent England.
He warmed to his task in Austria to help lock down a game in which Ireland grew increasingly confident as time wore on.
2. Martin O'Neill has strength in depth after all
The Republic arrived in Vienna without regular starters Stephen Ward, James McCarthy, Shane Long and Daryl Murphy and with back-up men Stephen Quinn and Eunan O'Kane also on the injury list. There was a near-audible groan from the away bench when holding midfielder Glenn Whelan limped off barely before breaking sweat, but Hull's David Meyler plugged the gap with such aplomb that the transition was almost seamless.
3. James McClean is improving
McClean's career to date has been eventful to say the least and a man who has been vilified off the pitch in England for refusing to wear a poppy at this time of year, despite an eloquent explanation of his reasons, is not everyone's cup of tea.
But he has matured as a player and three goals in his past two games for Ireland have resulted in six precious points, and his influence has not gone unnoticed by grateful manager Martin O'Neill.
4. Austria are better than their results so far suggest
Marcel Koller was left shaking his head as Austria slumped to a seventh defeat in 11 games since they romped through qualification for Euro 2016. They have managed to take just four points from their opening four fixtures, but had it not been for the crossbar repelling Marcel Sabitzer's first-half effort and a series of misses by striker Marc Janko, things might have been very different.
5. Roy Keane still terrifies people
Even as he raced in on goal to secure victory for Ireland, McClean admitted Roy Keane was in his head. He said: "If I had missed the target, Roy would have killed me. He hammers us in training that we must hit the target."