Barry Hawkins survived a remarkable fightback from Dominic Dale to seal a 13-12 victory and set up a semi-final against defending champion Ronnie O'Sullivan at the Dafabet World Snooker Championship.
Dale, trailing 11-5 overnight, claimed the first seven frames of the session to shock last-year's runner-up who needed just two further frames when play began on Wednesday afternoon.
He eventually got them, but they were the last two of the session as Hawkins set up a repeat of last year's final.
Dale took the first three frames of the day with breaks of 75, 65 and 64 before claiming a slightly scrappier encounter to go into the mid-session interval just two behind.
A break of 61 in the 21st made it 11-10 and the Welshman then prevailed from a long safety battle to level up the scores.
A 52 clearance in the next edged the player known as 'Spaceman' ahead and at that point it looked like momentum would carry him over the line but Hawkins is made of stern stuff and claimed his first frame of the day with a break of 66 took the match to a decider.
Both players were edgy in the opening stages but it was Hawkins who held his nerve with a 65 clearance to go through.
Earlier in the day, O'Sullivan admitted he was surprised with the "easy" nature of his victory as he demolished Shaun Murphy 13-3 with a session to spare.
The five-time champion capitalised on a host of mistakes from his opponent, and told BBC Two: "You just never know what type of match you're going to get.
"You can expect a really tough match and it turn out easy like it did with Shaun. I didn't expect to win it that easy to be fair. He's a free-scoring great potter.
"He just missed a few balls and let me in quite easily. I still had to pot them but I didn't have to fight for my chances."
O'Sullivan claimed seven of the eight frames on Wednesday after overcoming an early 2-0 deficit to lead 6-2 overnight.
The 38-year-old added the opening two in the morning to stretch his advantage before Murphy got a frame back in the 11th but O'Sullivan followed that with a break of 118 to take a 9-3 lead into the mid-session interval.
The restart was delayed for a short while due to a problem with the scoreboard and when play resumed O'Sullivan made a break of 59 before giving Murphy a glimmer of hope.
Murphy looked to be heading for a rare frame success but missed a routine pink and O'Sullivan gratefully took the opportunity to extend his lead further.
A missed green off the spot in the next summed up Murphy's performance as O'Sullivan again capitalised, closing out a comprehensive victory with the minimum of fuss.
Mark Selby also breezed through to the semi-finals after claiming the one remaining frame he needed against Alan McManus.
The Leicester cueman came into the session with a commanding 12-4 lead and veteran McManus won the opening frame with a break of 69 to extend the contest.
The Scot was among the balls again early in the 18th before losing position on 20, opening the door for Selby.
A missed red to the middle from the 2007 finalist allowed McManus back to the table but he could not take advantage and Selby closed out a 13-5 win to advance to a semi-final against either Judd Trump or Neil Robertson.
Trump leads world number one Robertson 9-6 and their match will be played to a conclusion on Wednesday evening.
The Australian trailed 6-2 overnight but claimed the first two frames of the session before a break of 57 gave Trump a three-frame cushion.
That became five as the Bristolian also won the next two but vital breaks of 50 and 57 closed the gap and set up a grandstand finish which will be played in a single-table setting after O'Sullivan's early conclusion.