Hull were forced to wait 20 minutes before their fate was determined. With just minutes to go in the Tigers' game, they were heading up against the Bluebirds yet an incredible finale with one red card, two penalties and a mini pitch-invasion left the door open for Gianfranco Zola's 10 men at Vicarage Road.
However, with their clash delayed due to an injury, they were unable to score the goal which would have sent them into the top flight and it was Ross McCormack who scored instead to give Leeds a 2-1 win and send the Tigers into delirium.
Former Hull loanee Fraizer Campbell had threatened to derail the Tigers' hopes by breaking the deadlock just after half-time, but two goals in five minutes through Nick Proschwitz and Paul McShane looked to have turned Hull's entire season back around.
Andrew Taylor was then sent off before Proschwitz had a penalty, which would surely have guaranteed promotion, saved. Instead, Nicky Maynard earned Cardiff a share of the spoils from the penalty spot although matters at Vicarage Road would ultimately transpire in Hull's favour.
The story's potential villain arrived at the start of the second half to throw a spanner in the works as Campbell broke the deadlock four minutes after the restart. The striker drifted between the two centre-backs to collect a long ball and, with just one touch, coolly rolled the ball beyond David Stockdale and into the corner.
However, nine minutes later, parity was restored. Stephen Quinn's ball from the left came into Proschwitz and he managed to just stay onside and steer the ball into the far corner with his left foot.
From a corner on the right, McShane got the wrong side of his marker and diverted Robbie Brady's inswinging delivery from the right into the bottom corner.
Few could have predicted what happened next. First Taylor was given his marching orders in the 90th minute for a foul on Ahmed Elmohamady then Hull had a stoppage-time penalty when Ben Turner crashed into David Meyler.
That prompted dozens of home supporters to spill on to the pitch and the delay clearly disrupted Proschwitz, who saw his spot-kick saved by Marshall.
And, just seconds later, Cardiff had a penalty of their own when the ball struck Abdoulaye Faye's hand. Nicky Maynard drilled the set-piece home to ensure Hull were left needing a favour at Watford, and they got just that from Leeds.