Martin Kaymer and last week's winner Thomas Björn took over at the top with dazzling runs as the Omega European Masters tried to beat the weather in Switzerland.
Kaymer, four behind Welshman Jamie Donaldson overnight, had two eagles and two birdies in the first eight holes to go two clear.
But Björn, three behind with a round to go just as he was in the Johnnie Walker Championship at Gleneagles, had four successive birdies from the fifth and when he made another from five feet at the tenth he joined Kaymer on 16 under par.
Rory McIlroy and Lee Westwood were two behind at the turn and joint third with South Africans Keith Horne and Jaco Van Zyl and also Swede Fredrik Andersson Hed.
Tee-off times had been brought forward because of the threat of storms, but low cloud was causing problems as the tournament entered its closing stretch.
Kaymer led by one again when Björn bogeyed the 12th and the World Number Five missed a golden chance to double his advantage, three-putting the long 14th for par. His second putt was only two feet.
That gave Donaldson extra hope as he had birdied the 11th and 12th to join Björn one behind, but McIlroy was three back after bogeying the tenth.
Kaymer also failed to birdie the long 15th, missing from five feet after going from rough to sand, and he was joined when Björn and Donaldson made their fours on the 595-yard 14th.
They came in different ways, though. While Donaldson two-putted, Björn was fortunate not to go in the pond on the right and holed from ten feet.
If that was lucky then his playing of the 15th certainly was not. He fired in a fairway wood over the guarding bunker to ten feet and made the eagle putt to lead by two at 18 under.
Suddenly he was on course to be the first back-to-back winner of The European Tour season.
