La Petite Coco lunged late to deny dual Classic heroine Love a return to winning ways in the Moyglare "Jewels" Blandford Stakes at the Curragh.
The Aidan O'Brien-trained Love looked a potential superstar in the making after winning the 1000 Guineas, the Oaks and Yorkshire Oaks as a three-year-old last season.
But while she came out on top on her seasonal reappearance in the Prince of Wales's Stakes at Royal Ascot in June, the daughter of Galileo had since failed to run up to expectations in the either the King George or the Juddmonte International, finishing third on both occasions.
Having her first start outside of Group One company in over two years, Love was the 6-5 favourite and everything looked to be going according to plan for Ryan Moore after she went a couple of lengths clear of the field early in the home straight.
However, Paddy Twomey's progressive filly La Petite Coco (16-5) - stepping up in class after an impressive success in the Group Three Give Thanks Stakes at Cork - gave chase and finished with a flourish under Billy Lee to get up and win by a short head.
Twomey said afterwards: "We hoped coming here that she might do something like that. The worry was the quicker ground and dropping in trip.
"I had a plan mapped out for her in my head and this was it. I wasn't expecting Love (to run), but when she turned up I said 'we're not changing course, we're going forward'.
"Barry Irwin (of owners Team Valor) gave me a bit of a lecture about taking on Love, but I told him I thought she was good and I thought she was good enough to take her on.
"The plan has been to go to Ascot (on Champions Day) for the fillies' and mares' race and I think a mile and a half is really her thing, not a mile and a quarter."
Big Gossey was a surprise winner of the Irish Stallion Farms EBF "Bold Lad" Sprint Handicap.
Charles O'Brien's 33-1 shot raced close to the pace throughout under Michael Hussey - and after taking over the lead inside the final furlongs, he dug deep for pressure to repel the challenge of Arnhem by three-quarters of a length.
"That was sweet," said Hussey.
"He travelled throughout and picked up well. I was in front a bit too early on him, but he gamed it out. He has plenty of speed and did everything right."