Three-time champion Mark Williams will take a 13-11 lead over Judd Trump into the concluding session of their World Championship semi-final on Saturday evening.
An absorbing morning of play started with the players level at 8-8 after Williams recovered from 7-3 down to rein in the world number one on Friday in Sheffield.
Williams, 50, who is bidding to become the oldest Crucible finalist, continued in the same vein, crafting four half-centuries as he took five of the eight frames on offer.
He opened up with a break of 57 and, while Trump responded with consecutive runs of 71 to edge back ahead, the Welshman then reeled off the next three frames.
Englishman Trump, who has won 30 ranking events and reached six finals this season, constructed a timely 64 to reduce his arrears to 12-11.
However, Williams, whom Trump defeated 17-16 in their thrilling last-four meeting in 2022, composed a 62 in the 24th frame of their best-of-33 encounter to give himself a two-frame cushion when play resumes at 19:00 BST.
