The mystery runner on Saturday's Flemington race card is a mystery no more.

Spending, a three-year-old filly who has been "hiding" in New Zealand for the past couple of years, turned her debut appearance into a showstopper, with a stunning win in the Nouvelle Star Handicap (1000m).

A sister to the city winner Shopaholic, Spending had been taught the basics of racing before she left owner Gary Chittick's Waikato Stud and has had the finishing touches applied during the five weeks she's been at Danny O'Brien's Flemington stables.

"She'd done what she had to do over in New Zealand," said stable foreman Paul Heazlett.

"They did a good job over there, she's pretty bullet proof."

Even for experienced horses the Flemington straight track can be a problem, but Spending ($8) coped admirably under James Winks, scoring by a long neck from Agulhas ($26) with a further three-quarters of a length to the favourite Octavia ($2.50) in third place.

Chittick retained Spending after passing her in at the sales when the bidding stalled at $300,000.

The filly by Pins from the O'Reilly mare Splashing Out is likely to be taken along slowly with a view to a spring campaign.

"Danny will have a look at her when he gets back from Queensland and he'll make the right decision," Heazlett said.