Millwall took a big step towards Wembley by coming from behind to win 3-1 at Bradford in the first leg of their Sky Bet League One play-off semi-final.
First-half goals from Lee Gregory, Steve Morison and Joe Martin turned the tie in the Lions' favour ahead of Friday's return game after the Bantams had taken the lead through Tony McMahon's early penalty.
There was a raucous atmosphere inside Valley Parade all afternoon, although it was temporarily subdued ahead of kick-off by an emotional minute-long applause in memory of former Bantam Chris Mitchell, who died earlier this month at the age of 27.
Spurred on by the vocal backing, the home side were given the perfect opportunity to seize the initiative when Lions left-back Martin handled in the box following Jamie Proctor's header across goal.
McMahon was perhaps lucky to still be on the pitch to take the penalty following a coming together with Millwall's Chris Taylor as he waited to take the kick. Referee Dean Whitestone opted to book the Bradford player and he duly stepped up to send goalkeeper Jordan Archer the wrong way with 13 minutes played.
The goal prompted the noise levels inside the stadium to increase further, but the City supporters were not smiling for long.
Lions top-scorer Gregory, on his first start since April 19 following a double hernia, controlled Morison's nod down in the area two minutes later and turned to fire his 26th goal of the season into the bottom left corner.
Filipe Morais then flashed a volley wide for Bradford before the visitors turned the game on its head 11 minutes prior to the break.
Shane Ferguson sent in an out-swinging corner from the left and captain Morison rose highest to head home off the underside of the crossbar.
Millwall are aiming for an immediate return to the Championship following relegation last season, and full-back Martin atoned for his early error by extending their lead in the final minute of the half.
Gregory was adjudged to have been fouled 25 yards from goal and Martin impressively curled the resulting free-kick past the dive of Bradford keeper Ben Williams and into the left corner.
Portuguese midfielder Morais should have reduced the deficit eight minutes into the second period but he somehow shot wide with the goal gaping after Proctor had robbed Carlos Edwards and teed him up.
Phil Parkinson's side, who have not been in the second tier since 2004, dominated the second period and defender Nathan Clarke almost scrambled the ball home following a corner.
Keeper Archer then had to be alert to tip over a header from Nathan Clarke, while Lee Evans curled narrowly wide from a free-kick from distance.
The Londoners offered little attacking threat after the break but their dogged defending was enough to ensure they take a two-goal advantage back to The Den.