Gary Wilson came from 3-0 down to lead Ali Carter 5-3 after the first session of their quarter-final clash at the Betfred World Championship.
Former taxi driver Wilson had never won a match at the Crucible before this year, but has shown his quality this time by knocking out Luca Brecel and Mark Selby.
World number 19 Carter, who was runner-up in Sheffield in 2008 and 2012, went 3-0 up with a top break of 135. But it was world number 32 Wilson who dominated from that point, winning five frames in a row with top breaks of 109, 86, 134 and 55.
On the other table, Kyren Wilson and David Gilbert finished all square at 4-4. Wilson has reached the last eight for the fourth consecutive year and is aiming for his second consecutive semi-final. Gilbert is in new territory as before this year he had only won one match at the Crucible.
World number eight Wilson took the opening frame by potting pink and black then Gilbert levelled with a break of 68. The next two frames were shared before world number 16 Gilbert made a 60 clearance to lead 3-2.
Wilson took the next two frames with top runs of 46 and 43, then Gilbert won the last of the session with an excellent 109.
Both matches resume at 7pm on Tuesday night and play to a finish on Wednesday. First to 13 frames earns a place in the semis.