Leicester showed impressive character, quality and resilience to recover from Jamie Vardy's sending-off and a West Ham comeback to eke out what could prove a crucial point in the race for the Premier League title.
Claudio Ranieri's men were supposed to be relegation fodder and odds of 5,000/1 underlined just how unlikely a title tilt looked to be, yet this has been one of the most incredible seasons in English football history.
The King Power Stadium faithful went through the whole gamut of emotions after goalscorer Vardy's controversial dismissal paved the way for West Ham to go ahead through Andy Carroll's spot-kick and a wonderful Aaron Cresswell strike.
But Leonardo Ulloa's stoppage-time penalty secured the Foxes a 2-2 draw.
The draw stretches Leicester's lead over second-placed Tottenham to eight points, but Mauricio Pochettino's men can cut the gap at Stoke on Monday as an amazing campaign heads towards a dramatic ending.
This never looked like being a straightforward afternoon after Kasper Schmeichel pushed a Cheikhou Kouyate header on to both posts inside the opening seconds before Vardy opened the scoring in the 18th minute.
However, the England striker's sending-off for simulation early in the second half blew the game wide open, with Winston Reid clipping a post.
Referee Jonathan Moss then further angered the home support by adjudging Wes Morgan had fouled the Hammers defender in the area.
Substitute Carroll slotted home the resulting spot-kick in front of watching England manager Roy Hodgson, who then saw uncapped left-back Cresswell highlight his quality with a sublime strike across goal and into the roof of the net.
There was another twist to come, though, as Moss pointed to the spot at the other end after ruling Carroll had taken down Jeffrey Schlupp and Ulloa held his nerve to equalise and send the Leicester faithful into raptures.
A huge roar met the final whistle -- a din that started from the outset and ratcheted up several notches after an extraordinary early let-off for the hosts.
Dimitri Payet's free kick was directed goalwards by Kouyate and was bound for the net until Schmeichel managed to tip the header onto the post, with the ball rolling across the line and hitting the other post before the Leicester goalkeeper gratefully grabbed it.
It was a remarkable moment that could have changed the outcome of this match -- and perhaps the title race -- and allowed the hosts to kick on.
Their movement in the box bamboozled the Hammers defence and Robert Huth headed a Marc Albrighton free kick just wide, before Danny Drinkwater tried his luck from distance.
The hosts' link-up play was as seamless as it was impressive and the 19th-minute opener was a classy team effort.
Riyad Mahrez collected a long throw from Schmeichel and fed N'Golo Kante, whose clever ball put Vardy through to hit a strike that rippled the net.
Leicester's three PFA Player of the Year nominees combined wonderfully for a goal that led to chants of 'are you watching Tottenham?'
The game become fractious as play was broken up by a string of free kicks, with Vardy and Reid soon getting booked.
The latter's claims for a penalty in the midst of that were ignored, before Mark Noble and Payet also found their names in the book.
Carroll replaced Pedro Obiang when the teams emerged for the second half and was quickly involved, heading wide five minutes after the restart.
The Foxes were soon threatening again, though, and Huth headed a Christian Fuchs cross wide, before Shinji Okazaki's low ball just evaded Vardy at the far post.
From nearly slotting a second, the England striker was soon heading for an early bath.
Latching onto a through ball, he got into a tangle with Angelo Ogbonna in the area and referee Moss adjudged the Leicester forward to have purposely taken a tumble and dished out a second booking.
The majority inside the King Power Stadium were incandescent with rage at the 56th-minute decision that Reid almost capitalised on, sending a Payet cross onto the post with a deft flick.
Emmanuel Emenike flashed a strike over as West Ham pushed for an equaliser that would arrive when Reid went down under pressure from Foxes captain Morgan.
Leicester fumed but Carroll kept his cool to slot home the 84th-minute penalty - a goal that was followed within two minutes by Cresswell's thunderbolt.
It was an exceptional strike that looked to have settled the match, only for Moss to once again point to the spot in stoppage time.
Schlupp went down under pressure from Carroll and Ulloa sent home the penalty, not that the officials were forgiven at the final whistle.