Perth staged a remarkable comeback to clinch an exciting eight-point win against Peel at Lathlain Park.
Trailing at each of the changes, the Demons got up off the canvas to post a 10.15 (75) to 10.7 (67) victory against the premiers of the past two years.
The Thunder led by 11 points at quarter time and half time, and were still ahead by 16 points at the last change before being overrun in the last term 4.7 (31) to 1.1 (7).
Midfielders Brant Colledge, Cody Leggett, Corey Yeo and Clint Jones were outstanding for the Demons along with defender Michael Sinclair and forward Cody Ninyette.
Leggett finished the match with 32 possessions, seven marks, five tackles and 13 inside 50s while Colledge was equally effective with 28 disposals, six marks, eight inside 50s and two goals.
The result pitch-forked Perth into fourth spot on the premiership ladder, strengthening claims for a first finals appearance since 1997.
Veteran midfielder Danyle Pearce and defender Michael Johnson improved their chances of a call-up to Fremantle with strong games for Peel.
Pearce was involved from the start of the game, collecting 14 possessions and ended the game with 34 possessions, four marks, five inside 50s and a goal.
The 32-year-old did well under the watchful eyes of Dockers hierarchy including coach Ross Lyon and football operations manager Chris Bond.
Pearce is expected to retire from the AFL at the end of the season and the classy left-footer would be hoping to push back into the Dockers side in coming weeks.
He has managed three games for Fremantle in 2018 to take his tally to 104 after notching 154 for Port Adelaide.
Pearce played his 250th match against Port Adelaide in round two last year but managed only seven for the year.
Johnson, another player expected to bow out of the AFL at the end of the season, also did well for the Thunder.
The 33-year-old marshalled the Peel defence, able to repel several Perth attacking moves when they threatened to seize control.
Peel started brightly, a vast improvement on the side that was restricted to a match total of 2.5 (17) in a 52-point loss to Subiaco at Leederville Oval in the previous round.
Fremantle squad member Brady Grey started the match full of running and kicked the Thunder’s first two goals, one either side of an accurate snap from livewire Demons forward Cody Ninyette.
Peel had four of the first five goals to race 16 points clear at the 16-minute mark of the opening quarter.
Pearce was starting to wield an influence, the Thunder ahead by 11 points at the first change.
The game developed into an arm wrestle in the second term, each team scoring one goal as the defences got on top.
It was more of the same at the start of the third stanza, Brant Colledge finishing accurately for Perth at the three-minute mark and Ben Hancock responding for Peel moment later.
Peel looked to have the match in their keeping at three-quarter time, only for Perth to kick 13 points clear after kicking the first four goals of the quarter.
Peel’s loss was further soured by a lower leg injury to tall utility player Michael Apeness.
PERTH 2.2 3.4 6.8 10.15 (75)
PEEL 4.1 5.3 9.6 10.7 (67)
GOALS – PERTH: Ninyette 3; Colledge, M Bennell 2; Cary, Leggett, Johnson. PEEL: Grey 2; Ugle, H Bennell, Hancock, Meek, Crowden, Tassone, D Pearce, Strnadica.
BEST – PERTH: Leggett, Colledge, Sinclair, Yeo, Ninyette, C Jones. PEEL: D Pearce, Johnson, Crowden, Hancock, Howlett, Power, Strnadica.
INJURIES – PEEL: Apeness (lower leg).
UMPIRES: R Shelton, J Wright, C Dugan.
CROWD: 1400 (approx) at Lathlain Park.