Sylvain Cloutier’s team staged a late fightback, but the main damage was done in the first period.
Danny Stewart put Fife ahead on the powerplay at 10.34 and it became 2-0 to the hosts when Casey Haines struck at 13.51.
The in-form Dominic Osman halved the deficit for Hull when he struck his 12th goal of the season just 12 seconds later, but the Flyers – who came into the game having lost nine of their previous 10 matches – restored their two-goal lead through Jason Pitton at 18.29.
It became a one-goal game five minutes into the second periopd when Stingrays’ Jereme Tendler scored following good work by Janis Ozolins and Jason Silverthorn.
Chances came and went at both ends, but the game-winning goal came in the 39th minute when Haines registered his second of the night.
Player-coach Cloutier gave Hull some slender hopes of taking the game into overtime when he made it 4-3 with just 39 seconds remaining, but Fife managed to hold on.
“A bad first period cost us,” said Cloutier afterwards. “It was a long trip and we were still on the bus but we should have been ready, there are no excuses.
“We made some mistakes and they capitalised. We battled back and kept going but it was a missed opportunity for us to get two more conference points.
“But we will regroup in practice this week and get ready for the weekend.”
On Wednesday, concerns over Flyers’ player-assistant coach Stewart, who had to be helped off the ice following a hit on the boards during the third period, seemed to have been allayed, after he was released from hospital.
“Danny is OK,” said Flyers player-coach Todd Dutiaume. “He is going to be observed for now, we are all relieved for him. It was good to get the win for him after what happened.”