Qualifier Gary Wilson produced an immaculate 140 break as he came out of the first session with Judd Trump level at 4-4 in their World Championship semi-final at the Crucible Theatre.
World number 32 Wilson had several chances, and may count himself unfortunate not to have an overnight lead from his joust with the Masters champion.
Wilson opened with a break of 61, but lost the first frame before edging a scrappy second frame and then piecing together a brilliant 140, the second highest break of the tournament behind Trump's 141 in the first round.
Trump made 54 to restore parity at 2-2 before he dominated the fifth frame for a 3-2 advantage.
Wilson was not perturbed as he established himself in the next two frames for a 4-3 lead. The Tyneside player had chances to open up a 5-3 overnight, but Trump finished matters off with a 54 after Wilson failed to slot the penultimate red with a spider down a side cushion.
They begin their second session at 2:30pm on Friday afternoon.
In the other semi-final, 16th seed David Gilbert continued his fine form to take an early 5-3 lead over four-times world champion John Higgins in Sheffield.
Higgins had beaten Neil Robertson 13-10 in an epic to reach the last four, but failed to click in an opening session that saw Gilbert play the better snooker.
A century break of 113 was the highlight for the Englishman, who won five of the six frames before the break to take an early lead with plenty of action still to come.