A week after kicking 0.4 in a shock western derby loss to West Coast, Banfield kicked two clutch goals in the dying minutes on Saturday night to secure the 14.11 (95) to 10.11 (71) win in front of 45,931 fans.
The result snapped a run of three straight losses for the Dockers, and improved their season record to 4-3.
The Bulldogs trailed by just six points with a little over four minutes remaining.
Banfield's 45m set shot gave Fremantle a 12-point buffer.
Then with less than two minutes remaining, Banfield nailed a tough 50m shot near the boundary line to secure the victory, with Michael Walters' late goal adding icing on the cake.
Banfield goes BANG to seal the deal!#AFLFreoDogs pic.twitter.com/9KRG7caYEs— AFL (@AFL) April 27, 2024
Banfield finished the match with three goals from 22 disposals.
"He was great. I said to him during the week that the hardest part about being a forward is getting shots on goal, not necessarily finishing them," Longmuir said.
"He probably missed a couple of uncharacteristic set shots last week.
"I think he's a really good set shot, so I told him that, and then to stand up under pressure and deliver when we needed it, was great."
Fremantle veteran Nat Fyfe wound back the clock with 37 disposals, seven clearances and a goal, while Caleb Serong (37 disposals, 17 clearances) set a new club record for clearances.
Dockers debutant Cooper Simpson, who was subbed into the game in the second quarter, showed flashes of brilliance and finished with three score assists.
Fremantle spearhead Josh Treacy was superb with three goals and a whopping five contested marks.
Bulldogs utility Bailey Dale continued his resurgence with 30 disposals and two goals, while Sam Darcy kicked three goals.
Liam Jones was a spoiling machine in defence for the Bulldogs.
Bulldogs forward Rhylee West could be in trouble for a high shepherd that struck Brandon Walker in the head, resulting in the Dockers defender being assessed in the change rooms for concussion.
The Bulldogs suffered a blow before the match when midfielder Tom Liberatore, who was due to return from concussion, was ruled out through illness.
"He came over healthy and then somewhere between dinner and going to bed last night he fell ill," Bulldogs coach Luke Beveridge said.
"So I can't tell you whether it's food poisoning or he's just got gastro from something else ... but he just wasn't well enough to play."
The loss was compounded when forward Cody Weightman appeared to dislocate his left elbow again when he landed hard from a marking contest in the first quarter.
Fremantle also lost a player in the opening term, with Josh Draper suffering a game-ending hamstring injury.
The Dockers' midfielders feasted early as the Bulldogs struggled to cover the absence of Liberatore.
Fyfe racked up a career-high 15 possessions in the first quarter - 12 of which were handballs - while Serong (13 disposals) and Andrew Brayshaw (13) were also prolific.
Treacy's goal after the quarter-time siren gave the Dockers an eight-point edge, and the second term was an arm wrestle as momentum ebbed and flowed.
The Bulldogs controlled large portions of the third quarter, but their return of 2.7 let Fremantle off the hook, with Marcus Bontempelli missing a sitter of a set shot from 10m out.
The match was on a knife's edge in the last quarter before Banfield broke the Bulldogs' spirits with two late goals.
