Two dramatic tries in the final three minutes gave Wigan Warriors a thrilling victory which kept their top-four dream alive.
Anthony Gelling and John Bateman both crossed in a surreal finish to a scrappy game which had seesawed, exploded at one stage, and appeared to have slipped from the Warriors' grasp.
Mahe Fonua, the two-try curse of Wembley, returned to haunt them with another double - including a second which put 12-man Hull 22-20 ahead.
Wigan desperately tried to conjure a match-winning play, but didn't appear to have the time or the strike-power to snatch the win.
But then, with three minutes to go, Gelling cut through on Wigan's right to hush the home crowd - and trigger a spontaneous rendition of 'man of the people' from the travelling fan.
George Williams couldn't convert, leaving the visitors with a nervy two-point margin. But Bateman eased their nerves with a mazy run to the line to secure the vital two points - and claim their first win against FC in four matches this year.
Had Wigan lost, it would probably have ended their hopes of snatching a top-four spot, given Saints' superior for-and-against and what appears an easier run-in.
Now, they know if they win their next two matches, against Castleford and Wakefield, they will be guaranteed a place in the play-offs.
Last week, in a 26-16 win at St Helens, there was a swagger to Wigan's performance. This was a step-back. They let a 14-point lead slip into a two-point deficit, their last-plays were often poor, and they faded in the second-half against opposition playing with only 12-men.
Hull prop Liam Watts was sent off midway through the first-half for leading with the elbow into Micky McIlorum, who was benched and played no further part.
Wigan already had an 8-6 advantage at that stage, but failed to build on it before half-time as the home side rallied and rushed and frustrated the visitors' attack.
Shaun Wane's outfit appeared to take control with tries by Anthony Gelling and Tom Davies by the 50th minute mark, opening up a 14-point margin - before FC battled back to take the lead.
The tension was crackling before kick-off.
Like at Wembley, Liam Marshall was called up with less than half-an-hour's notice - this time Joe Burgess withdrawing from a warm-up injury (groin). Elsewhere, Tom Davies and Ryan Sutton returned.
The hosts had a clutch of key players missing, forcing Lee Radford to field a largely inexperienced bench and a makeshift backline.
Like a week earlier, Wigan started at a quick tempo. Oliver Gildart forced an early repeat-set, but Gelling released the pressure-valve with a wasteful pass which was gratefully picked off by Mark Minichiello. A subsequent penalty gave Marc Sneyd an early chance to nudge the hosts ahead, from 44m out - which was greeted by the usual chorus of 'Sneyyyyddddd' from the FC faithful.
Wigan replied in the eighth minute, a looped dummy-half pass to Liam Farrell allowing him to send Gildart through a stretched defence. In the build-up, Sam Tomkins had irritated the FC fans - setting the tone for the needle which was to follow.
Fonua swatted off Marshall's attempted tackle and plunged the ball down to lock the scores with a 12th minute try. Slowly, both sides stopped scoring tries and started skirmishing instead.
First, Josh Griffin was placed on report for an alleged dangerous tackle around the knees of Bateman, and moments later there was an all-in. Once it had calmed down, Williams struck a penalty to put Wigan 8-6 up.
Robert Hicks frequently spoke to captains Sean O'Loughlin and Danny Houghton, but his words did little to ease the tensions. It was getting nasty, or tasty, depending on your viewpoint. But when McIlorum was floored tackling Watts, Hicks showed the FC prop a red-card.
Down to 12, FC improved to cover for the numerical disadvantage, and there was no further scoring for the rest of the opening half. There were moments of excitement, a few crunching tackles and plenty of noise from the vocal fans, but neither side finished their sets particularly well.
With five minutes to the break, Wigan were awarded a penalty - Brad Fash pinged for preventing Liam Farrell from playing the ball - but Williams's 40m attempt sailed wide.
They didn't need to wait too long for the chance to extend their advantage, Gelling picking off a Sneyd pass and running clear to the line as the travelling fans chanted: 'Man of the people'.
If Gelling's try-celebration - a 'basketball shot' over the crossbar - didn't annoy the home fans, his next major play did; a pass which appeared forward which sent Davies to the line.
Williams hit one of the conversions, to put Wigan 20-6 up with half an hour to play.
They had a chance to extend their lead moments later, too, but a sweeping attack on the left broke down. Scrappy passages from both sides followed - the stakes, rather than the quality, held the interest. That was until Sike Manu powered through for a try on the hour-mark which, converted by Sneyd, cut Wigan's lead to a nervy eight-points.
Suddenly, the scoreboard generated the interest.
And with FC showing admirable energy, while a man down, they went over again when Sneyd raced onto an angled grubber and converted his own try to make it 18-20 with 15 minutes to go. Wigan continued to fade, allowing FC to make easy metres and time to pick their kicks. When Tomkins failed to defuse one high-ball, it provided the opportunity for man-mountain Fonua to cross for his second and send them two points up - Sneyd missed from the sidelines.
It left Wigan with eight minutes left to try and salvage the game - and, probably, their top-four hopes.
Like at Wembley, the scoreboard prompted them to put some width on their attacks. They forced a drop-out, and then another, but didn't appear to have the creativity to penetrate FC's desperate line.
And then up stepped Gelling to ruin the night for Hull, and the St Helens fans watching on TV, before Bateman added the crowning glory.
Hull FC: Shaul; Fonua, Connor, Thompson, Griffin; Kelly, Sneyd; Taylor, Houghton, Bowden, Minichiello, Manu, Watts. Subs: Washbrook, Turgut, Fash, Matongo.
Wigan: Tomkins; Davies, Gelling, Gildart, Marshall; Williams, Leuluai; Nuuausala, McIlorum, Clubb, Bateman, Farrell, O'Loughlin. Subs: Powell, Tautai, Sutton, Isa.
Referee: Robert Hicks
Star man: John Bateman