Hull FC scored 24 unanswered points in the last 15 minutes to come from behind and defeat Harlequins.
Two tries apiece saw the sides level at 12-12 at half-time, before Tom Briscoe edged the visitors in front.
A seven-minute spell where Luke Dorn, Luke Gale and Chad Randall all crossed looked to have Quins set for victory.
But scores from Epalahame Lauaki, Sam Obst, Jordan Turner and Kirk Yeaman, all improved by Danny Tickle, gave Hull their first away win of the season.
It was Tickle who opened the scoring in warm sunshine at The Stoop, benefiting from good work by Joe Westerman to stroll over the line.
But Quins hit back, as first Dorn and David Howell combined to squeeze Chris Melling in, then, after Dorn's break, Tony Clubb burrowed over.
Richard Agar's Hull levelled on the half-hour mark, Yeaman running clear, and the Black and Whites moved into the lead shortly after half-time when Briscoe took advantage of some poor tackling to cross with ease.
The home side fought back again, with returning hooker Andy Ellis breaking away to set up Dorn, Gale kicking his third of five goals to put Quins in front once more.
Gale claimed a Dorn kick and touched down to stretch the hosts' lead and, when Karl Pryce marched through four tackles to put Randall over, Rob Powell's men looked on course for victory.
However, any thoughts they had of coasting to a win were cast aside when Lauaki burst over and, soon after, Obst crossed after good work from Sean Long.
And, with the clock running down, the lead changed for a fifth and final time as Turner and Yeaman each raced clear to earn Hull only their second win of the year.
Harlequins coach Rob Powell: "We had it won and then threw it away and that is just not acceptable.
"We have to be able to put games to bed and that is something we need to learn as a side.
"Panic set in at times at the end and we started conceding penalties and that really cost us.
"We have to learn to be a lot smarter as we controlled the game for spells and deserved more."
Hull FC boss Richard Agar: "We need this result to be a catalyst for us.
"We know we have the ability, it is all about getting the consistency.
"To get to that point in the game and then find the energy to come back and win like that is a massive testament to the boys.
"The biggest thing for me is that many sides would have given up at that stage but we didn't.
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