Six strokes clear during his third round Fisher fell back from 16 under par to 11 under and was overtaken by Australian Richard Green and home favourite Padraig Harrington.
But then came an 18 foot eagle putt on the long seventh and birdies at the ninth and tenth to put him back on course for the first prize of €500,000 - and a rise from 13th to sixth in the Ryder Cup race.
After 11 holes Harrington was sharing second spot with Spain's Gonzalo Fernandez-Castaño and Fisher's compatriot Chris Wood, while Green was one further back.
Harrington and Green cut the gap to two with birdies at the 15th - and then to a huge roar Harrington made a nine foot eagle putt on the next to join the lead again.
Green two-putted it and was only one behind.
Fisher responded brilliantly with an approach to three feet at the 15th and when he two-putted the long 16th for another birdie he was two in front.
Harrington missed a ten foot chance at the 17th, failed to hole from 25 feet on the last and posted a superb 64 for 16 under, but it looked as if it was not going to be enough.