Aidan O'Brien's Misty For Me secured her second Group One haul with a battling effort in the Total Prix Marcel Boussac at Longchamp.
The Moyglare Stud Stakes heroine was always well to the fore in the hands of Johnny Murtagh but seemed set for minor honours when hot favourite Helleborine cruised up menacingly inside the final two furlongs.
The latter looked like running away with the contest when quickening up smartly to join Misty For Me, but O'Brien's filly was in determined mood and found enough for pressure to pass the post in front.
John Gosden's Rainbow Springs ran a big race in third to give a nice boost to the form of Frankel, who beat her out of sight at Doncaster recently.
O'Brien said: "She's a very good filly. She's an Oaks and a Guineas filly next year - she could do both.
"She won her maiden over six furlongs and is by Galileo out of a Storm Cat mare."
Murtagh said: "I was a bit worried about the ground but she was very relaxed and she found plenty for me. She's won two Group Ones now, so she's a grand filly.
"This is a race all the great fillies have won and hopefully she can come back and do it again next year.
"She's not short of speed but I'm confident she will get the mile. I hope she stays a mile and a half and if she does, she'll be a real Classic prospect.
"The Guineas is always a good starting point and I'm sure Aidan will have her in the right races."
Paddy Power make Misty For Me the 6-1 favourite from 7s for next year's 1000 Guineas while the filly is 8-1 for the Oaks.