NORWICH's resilience was broken in the 89th-minute against Leicester City with Leonardo Ulloa's heartbreaking winner for the title-chasing hosts.
City, playing with three central defenders, more than matched the league leaders throughout at the King Power Stadium but Ulloa's stabbed home Marc Albrighton's cross to settle an even game.
Alex Neil's team had worked hard for a precious point in the Premier League survival battle, with Cameron Jerome going closest for the Canaries with a first half header.
Three changes were made from the 2-2 draw with West Ham a fortnight ago as Neil reverted to a 3-4-3 system.
Ryan Bennett was included the eleven with Sebastien Bassong absent from the matchday squad. Ivo Pinto was employed at wing-back, while Alex Tettey returned from suspension.
Leicester were without the suspended Danny Simpson, with January signing Daniel Amartey brought in for his full Foxes debut.
The home team saw most of the ball early on but Jerome was presented with a chance on nine minutes when he was picked out by Nathan Redmond on the counter-attack, but a poor touch allowed Kasper Schmeichel to clear up.
Leicester turned the screw with a sustained spell of pressure - first Bennett did well to block Shinji Okazaki's clever flick from Jamie Vardy's cross, before Russell Martin nearly turned the ball into his own net from Marc Albrighton's delivery.
Albrighton himself curled an effort over from 20 yards, but City will have been content with how solid they looked against Leicester's incisive attack.
Straight from a set-piece, Ruddy saw Albrighton's delivery whistle narrowly wide of his post, but the Canaries had a great chance seven minutes before the break.
Robbie Brady delivered a superb set-piece and Jerome rose to meet it, but the striker guided his header the wrong side of Schmeichel's post.
Redmond then forced a low save from the Foxes' goalkeeper as Neil's men finished the half strongly - though at the break it remained goalless.
HALF-TIME: Leicester City 0-0 Norwich City
The Canaries started the second half well, and were more than matching their opponents for sharpness and physicality.
Ruddy make a comfortable save after Vardy was teed up from a free-kick, but there was certainly some tension in the air as the league leaders looked to extend their momentum from this extraordinary season.
As the match entered its final third, it remained difficult to call, with both teams harbouring ambitions of getting the three points.
Claudio Ranieri was the first to blink as he made a double substitution with 20 minutes left - off came N'Golo Kante and Okazaki to be replaced by Andy King and Jeffrey Schlupp.
Huth nodded a tame header wide under pressure from a corner and Vardy turned a Schlupp cross wide off his shoulder - but still the deadlock wasn't broken.
Norwich had an opportunity when Redmond was fouled by Christian Fuchs, but Schmeichel did well to punch Brady's pacey delivery clear.
Redmond then arrowed a drive towards goal from 25 yards, but it flashed just wide with the City supporters at that end on their feet.
Then there was heartbreak for City in the penultimate minute of the game - Albrighton was set free down the right, and substitute Ulloa converted at the back post to send the home crowd into delirium.
City's own sub Patrick Bamford sliced a shot wide from the edge of the area, and Leicester saw out the rest of stoppage time for a priceless win.
FULL-TIME: Leicester City 1-0 Norwich City
GOALS: Foxes: Leonardo Ulloa (89)
LEICESTER CITY: Schmeichel; Amartey (Ulloa 78), Huth, Morgan (c), Fuchs; Mahrez, Kanté (King 70), Drinkwater, Albrighton; Okazaki (Schlupp 69), Vardy. Subs not used: Schwarzer (GK), Gray, Dyer, Wasilewski.
NORWICH CITY: Ruddy; Bennett, Martin (c), Klose (Mbokani 90); Pinto, Tettey, Howson, Brady; Redmond, Naismith (Jarvis 82), Jerome (Bamford 90). Subs not used: Rudd (GK), Mulumbu, Olsson, O'Neil.
REFEREE: Neil Swarbrick