The Broncos will now play Canberra away in the first week of the finals and get a crucial second chance in the semis thanks to a 22-point haul from Walsh, which included two tries and seven goals.
The mercurial Broncos No.1 put the drama of the week's 'Toiletgate' saga behind him to have a blinder on Thursday.
"He did OK, I don't think you'll have to worry about toilets," Broncos coach Michael Maguire grinned.
"He's a character, and obviously creates a lot of noise, but at the end of the day he's in here training and doing all the work with the players and he wants to win."
It was just the Broncos' second win in their past 19 games against the Storm, but their ninth victory this season from the last 11 matches.
Hughes had just returned to action after missing five weeks with a shoulder injury.
"I'm not quite sure if it's the wrist or just halfway on the forearm," coach Craig Bellamy said.
"They pretty much think it's a break without a doubt, he's in plaster already, so that wasn't a great idea to put him back this week. I'd imagine it's season-ending."
In front of a sold-out crowd at Suncorp Stadium, he went to tackle Broncos forward Brendan Piakura and immediately clutched at his left wrist.
Hughes, last year's Dally M Medal winner, went up the tunnel in the 25th minute and his side's finals hopes possibly went with him.
To make matters worse prop Nelson Asofa-Solomona was put on report and sin-binned for a high shot on Ben Talty.
The Storm will face a nervous wait for the MRC charge sheet as the giant forward has two prior offences on his record.
A grade-two high tackle or dangerous tackle charge would lead to a three-game ban. If second-placed Melbourne win in the first week of the finals, such a charge would rub him out of the finals.
Walsh landed a 40/20 and celebrated his second try just after halftime with a slurping gesture.
It was a reference to the drink he had during the week from an unused toilet bowl installed in his home, which he posted to social media.
The Broncos called it, in a statement, a "poor attempt at humour" but there was nothing poor about his display. It was pure class.
Cheeky Walsh had also posted an image of himself on social media dressed up as a plumber. He certainly found leaks in the Storm defence and a pipeline to the tryline.
The Broncos were all over an ill-disciplined Melbourne early to take a 2-0 lead. The home side's defence, with No.6 Billy Walters notable, was on song.
Walsh opened the scoring after putting Payne Haas in a gap and supporting.
Storm second-rower Eliesa Katoa scored off a Cameron Munster bomb but Walsh found back-rower Brendan Piakura on the short side to extend the Broncos' lead on the cusp of halftime.
Both teams were down to 12 men in the first half with Broncos winger Deine Mariner binned for repeated ruck infringements.
Walsh extended the lead to 18-4 after the break. The Storm hit back with tries to winger Will Warbrick and centre Nick Meaney but it was too late. Broncos winger Josiah Karapani sealed it with the last play of the night.
The Broncos had axed centre Gehamat Shibasaki during the week for disciplinary reasons but it did not impact their display.
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