When the Dolphins led 28-14 in the 50th minute at Suncorp Stadium the Broncos were ninth on the live ladder. They finished Saturday in sixth, with the Dolphins dropping to ninth.
Walsh landed a 40/20 to turn the game in his best performance of the year, and possibly career, to win the "Battle Medal" as player of the match. With captain Adam Reynolds and his halves partner Ezra Mam out injured, Walsh took it upon himself to be the creative force.
"Tonight, he really got the balance right," Broncos captain Pat Carrigan said of Walsh.
"He's done some really special things but at the end of the day, we just need Reece Walsh to be Reece Walsh. He was massive for us."
The 23-year-old marshalled all the genius in his skillset to inspire the comeback. Veteran half Ben Hunt stood up with three try assists in the second half as 'Battle of Brisbane' specialist Kotoni Staggs scored a double in another blockbusting display.
Both teams were without key personnel but had plenty of men stand up.
Dolphins fullback Trai Fuller, recalled for his first NRL game of the season, scored a 75m individual try for the ages in the opening set after halftime.
The scores were locked at 14-all when the pocket rocket brushed through Pat Carrigan and Jordan Riki in a blistering run.
"Trai was brave. That inspires the other players," Dolphins coach Kristian Woolf said.
"They love the way he returns the ball and the way he just commits his body so much and brings so much energy. His first game back in NRL I thought he was outstanding."
Hooker Jeremy Marshall-King darted over from dummy-half for a 28-14 lead, but the Broncos weren't done.
Walsh, who had kicked the ball out on the full from a restart moments earlier, then landed the crucial 40/20.
"That 40/20 changed the game," Dolphins captain Isaiya Katoa said.
Brisbane winger Deine Mariner scored from the next set thanks to a masterful Hunt pass and it was game on.
There was better to come when Walsh started another raid on the last tackle. Five-eighth Billy Walters sent an immaculate cross-field kick for winger Josiah Karapani to finish a sensational team try.
Hunt conjured a slick grubber for prop Ben Talty to dive on and the Broncos incredibly had a 32-28 lead.
In the first half, Walsh set up a try for Staggs and started and finished a 55m attacking raid in cahoots with centre Gehamat Shibasaki.
The Dolphins had six of their first-choice pack out due to injury or suspension but second-rower Kulikefu Finefeuiaki and bench prop Josh Kerr provided impetus.
Hamiso Tabuai-Fidow, switched to the centres, had several electric moments and a classic battle with Staggs.
The man known as "Hammer" ran a lovely line after Katoa double-pumped and threw him a classic out-ball.
The Dolphins did well with limited opportunities and centre Jake Averillo burnt opposite number Shibasaki for a first-half try.
Brisbane second-rower Jack Gosiewski was ruled out of the match with an AC joint injury in the 12th minute.
The home crowd of 44, 350 were treated to the most enthralling derby of the six played so far.
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