Rory McIlroy moved into a five-way share of The Open lead, which included Jordan Spieth, as Tiger Woods' challenged faded fast at Carnoustie.
An incredible championship was headed for a remarkable finish, with McIlroy sinking a mammoth eagle putt at the par-five 14th that left him six under par.
The Northern Irishman had endured a mixed day until then, with three bogeys and two birdies through his first 13 holes.
Overnight co-leader and defending champion Spieth was at the same score having dropped three shots in the space of two holes at the fifth and sixth, while Francesco Molinari, Kevin Chappell and Xander Schauffele were also six under.
Woods was going great guns having made birdies at the fourth and sixth, and he briefly led outright at seven under.
But a costly double bogey at 11 was followed by another dropped shot at 12 and he was two strokes back.
Justin Rose was on the rise thanks to an eagle at 14 and he was five under, the same score as clubhouse leader Eddie Pepperell.