Laois came good when it truly counted, and under the most intense pressure, to prolong their interest in the All-Ireland SHC and secure their Liam MacCarthy Cup status for another season.
Paddy Purcell's two goals and 2-02 haul was ultimately decisive at the end of an epic preliminary-round tie at Parnell Park as Laois secured their first win of 2021.
Pointless in their Division 1 group in the league and hammered by Wexford in the opening round of the Leinster championship, Laois gave their best display of the year to avoid dropping back down to the Joe McDonagh Cup.
But they were made to fight all the way by a determined Antrim side that reduced an 11-point deficit after 41 minutes to just two at the second water break.
Laois also lost Ross King to a 49th minute red card and were temporarily down to 13 players as full-back Sean Downey was sent to the sin-bin in the 45th minute.
But Antrim were unable to push on beyond that two-point barrier as Laois outscored them by 1-06 to 0-05 in the final quarter to secure a landmark win.
Laois hadn't previously won a game with Plunkett in charge since April of 2016 when they beat Westmeath in a relegation play-off to stay in Division 1 but will now go into Monday morning's qualifier draw.
They will complete their 2021 campaign against Westmeath in August with the Leinster counties set to meet again in a Division 1 relegation decider.
Laois will fancy their chances after this all action display. They were on it from the very beginning, Podge Delaney booming over the opening score after just 10 seconds. King added a second shortly after and straight away Laois were up and running.
Charles Dwyer was their only forward that didn't get on the scoresheet in the first-half - though he rectified that late on - as Laois pinned Antrim down with a relentless vigour.
There were unanswered bursts of three and then four points in a row to open up a 0-11 to 0-04 lead at the first water break.
Ciaran Clarke, James McNaughton and Conal Cunning responded with Antrim scores to cut the deficit to four.
But Laois took off again and hit the interval with a commanding 1-17 to 0-10 lead, the crucial goal coming from Purcell in stoppage time.
It was a score that summed up both their industry and craft, Antrim midfielder Ciaran Johnston hustled and harried into losing possession and Purcell eventually running clear and planting a shot in the top right corner.
It was a terrific score though was outdone by Scully's suptumous lineball conversion from beyond the 65m line.
Scully repeated the feat from closer in though from the opposite side of the field in the third quarter as Laois kept the pressure on, twice moving 11 points clear.
An already exciting game reached fever pitch in the run up to the second water break as Antrim came strongly into the contest, dramatically reducing the gap to just two.
Sub Eoin O'Neill scored both goals, Cunning feeding him for the first and Clarke tapping down a long ball in for the second.
Antrim also had a penalty awarded during this blitzkrieg but Neil McManus's shot was tame and easily saved by Enda Rowland.
Still, the penalty arose from a Downey foul on Conor Johnston which resulted in a 45th minute yellow card sin-binning for the Laois defender.
Four minutes later, talisman forward King was dismissed for his second booking and suddenly Laois were under massive pressure.
All of that pressure was relieved for Laois by the second water break as they gathered themselves and returned the brighter, Purcell's second goal approaching the hour mark allowing them to breathe out.
Laois: Enda Rowland; Donnchadh Hartnett, Sean Downey, Lee Cleere; Podge Delaney (0-03), Ciaran McEvoy (0-01), Ryan Mullaney; Fiachra C Fennell (0-01), Jack Kelly (0-03); Paddy Purcell (2-02), Willie Dunphy (0-03), Ciaran Collier (0-01); Charles Dwyer (0-01), PJ Scully (0-10, 0-07f, 0-02 s/l), Ross King (0-02).
Subs: James Ryan for Mullaney 53, Eanna Lyons for Collier 58, James Keyes for Purcell 65, Aaron Dunphy for Willie Dunphy 72, Ciaran Comerford for Dwyer 75.
Antrim: Ryan Elliott; Damon McMullan, Stephen Rooney, Gerard Walsh; Eoghan Campbell, Paddy Burke, Aodhan O'Brien; Keelan Molloy (0-03), Ciaran Johnston; Neil McManus (0-04), Michael Bradley, James McNaughton (0-02, 0-01f); Conor Johnston (0-01), Conal Cunning (0-02), Ciaran Clarke (0-08, 0-07f, 0-01 65).
Subs: Aaron Crawford for McMullan 18, Joe Maskey for Campbell h/t, Eoin O'Neill (2-00) for Bradley h/t, Shane Elliott (0-01) for Conor Johnston 59, Matthew Donnelly for O'Brien 71.
Referee: Sean Cleere (Kilkenny)