John Higgins opened up a slender 13-11 advantage over Shaun Murphy heading into the final session of their World Championship semi-final at the Crucible Theatre.
Four-time champion Higgins, who turns 51 later this month, had not led at the end of a session throughout the tournament but picked the ideal time to change that as he bids to reach a record-equalling ninth final in Sheffield.
Higgins, who started the day strongly but was repeatedly pegged back by 2005 winner Murphy, ended it in the same fashion as he compiled his first century of the contest to hold sway.
The concluding chapter of their best-of-33 encounter will begin on Saturday at 14:30 BST, with the winner playing either China's Wu Yize or Northern Ireland's Mark Allen in the final.