Brisbane are within one win of the NRL grand final, after Ben Hunt slotted a 93rd-minute field goal to kick the Broncos to an epic 29-28 qualifying final victory over Canberra.

On a day of utter madness at GIO Stadium, Reece Walsh was sin-binned for a head-butt before engineering one of the most unlikely finals comebacks in memory.

Fresh off flipping the crowd the bird on the way off the field, Walsh returned from the sin bin to lead the Broncos back from 28-12 down with 14 minutes to play.

The Broncos star first went 40 metres to score a try of his own, set up a second with a pass for Jordan Karapani, then kicked a massive 40-20 in the lead-up to another.

Then with Brisbane down 28-26 and the siren about to sound, the Brisbane fullback had his leg taken by Zac Hosking as he attempted a two-point field goal.

It allowed Walsh to level the scores with a penalty from under the posts, before a frantic 10 minutes of extra time where neither side could break the deadlock.

With the match in golden point, Canberra thought they had won it when Jamal Fogarty crossed, before the bunker spotted a Jed Stuart knock on in the lead-up.

From the next set, Brisbane went downfield and Hunt nailed a field goal from 38 metres out to seal the match and send the Broncos to week three of the finals.

There they will meet the winner of Canterbury and Penrith at Suncorp Stadium, while Canberra will face Cronulla at GIO Stadium next weekend.

Reece Walsh is sent off for a head-butt. Photograph: Lukas Coch/AAP

Walsh’s effort to claim the title of ultimate pantomime villain was just the beginning of the drama on Sunday, as the Broncos threatened to unravel in the second half.

Upset by a Hudson Young celebration, Walsh pushed his head into the Canberra second-rower’s forehead before both were sin-binned.

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Brisbane captain Pat Carrigan then followed moments later for a shoulder charge on Morgan Smithies, that could well land him in trouble at the judiciary.

And at the same time, Canberra looked certain to run away with the match courtesy of fullback Kaeo Weekes.

After already giving Canberra an 18-12 half-time lead just before the break, Weekes went 95 metres to score his second when he scooped up a loose ball with Walsh off the field.

Ethan Strange then stepped Brisbane’s 11-man defence shortly afterwards, and at that point it was 28-12 and the Raiders looked home.

But no one at GIO Stadium could have predicted what would come next, with Walsh going from zero to hero and Brisbane claiming an epic finals win.

Beyond judiciary dramas, Brisbane will also sweat on a left ankle injury suffered by Payne Haas, who battled on to finish the match.

Second-rower Brendan Piakura is also in doubt for the preliminary final after suffering a suspected fractured eye socket.