One day last November, Toronto art dealer Odon Wagner received what may have been the most important phone call of his professional life. A client living on Ontario's Lake Simcoe said that he wanted to sell a painting from his collection.

Not just any painting, but an oil on canvas by John William Waterhouse, the leading artist of the so-called Victorian school. According to Dennis Lanigan, owner of one of Canada's largest collections of pre-Raphaelite art, Waterhouse "is the greatest of the Last Romantic artists and, as a painter, he towers over every other English painter of his generation."

The work was signed and dated -- 1909 -- but untitled, a fact that only added to its mystery and allure.

Wagner soon drove up to see it for himself. "It was like coming into Chartres," he recalls, "an overwhelming and magnificent experience."

Now, almost a year later, Waterhouse's painting -- Gather Ye Rosebuds while ye may -- is scheduled to be auctioned at Christie's in London in November. The presale estimated price is $2.9-million (U.S.) to $4.2 million, but most experts believe the final bid will be two or three times those numbers.

The excitement is the result of three factors -- the enormous boom in art values that's been experienced since 9/11, the particular appreciation in prices for Victorian art over the past five years and the serendipitous emergence of Waterhouse's canvas, which had been considered essentially lost by art historians.

Indeed, there were only two clues to its existence -- an illustration in a book about Waterhouse by Anthony Hobson and a tiny black-and-white photograph, published in Studio Magazine in 1911. It was this photograph that helped Odon Wagner and others identify the canvas -- although it took another three months of painstaking analysis and research to verify that it was an original Waterhouse and to assign it a fair market value.

Measuring 101 by 82.5 centimetres, the painting is thought to be the only Waterhouse work that is not rectangular. The top portion is arched, probably -- argues Brooklyn Museum Waterhouse expert Peter Trippi in an essay included in a book about the work published by Christie's -- at the request of Brodie Henderson, a younger brother of Waterhouse's principal patron, Baron Faringdon, a 19th-century British financier and railway tycoon.

Trippi, who spent hours examining the canvas, delayed publication of a new book and rewrote a chapter to include material pertaining to the discovery.

But the provenance of Rosebuds still has some significant gaps. It originally belonged to Henderson, but how and when and with whom it arrived in Canada is unknown. The back of the painting contained a fragmentary label from the Fine Art Galleries of the T. Eaton Corp., suggesting that at least one owner may have purchased it there. It also had the words "CAV Oct. 28, 1959, Frank Worrall," indicating that it was cleaned by Worrall (a Toronto restorer) at that time.

"Interestingly," Wagner says, "this painting is not mentioned in Worrall's ledgers as having being cleaned," although he was known for keeping meticulous records.

The current owner (who prefers anonymity) acquired the painting when he bought a Lake Simcoe estate and its contents in 1973. The prior owners have not been disclosed.

Wagner, in the business for 32 years, says the current runup in prices for beautiful art is not surprising.

"To the chagrin of critics, paintings that please and give happiness, like a beautiful largo in music, the more troubled the world becomes, the more their appeal increases. People [want] to surround themselves with works of quality that evoke contemplation, meditation and messages of quiet and peace."

In valuing the painting, Wagner was guided in part by the June, 2000, sale of another Waterhouse work, St. Cecilia. Estimated at £2.5-million ($3.9-million U.S.) to £3.5-million, it sold at Christie's for £6.6-million -- a world record at auction for a Victorian painting.

The Gather Ye Rosebuds painting, collector Lanigan says, "while a very attractive painting and one that I would be happy to own, is hardly one of the masterpieces of Waterhouse's late career."

Canada, he says, has "at least one Waterhouse painting of the first rank, the stunningly beautiful I am Half Sick of Shadows of 1915, in the collection of the Art Gallery of Ontario."

Before the Rosebuds work could be approved for export, it had to be offered for sale to Canadian institutions; there were no takers.

Never before exhibited to the public, the painting is now scheduled to go in display at Christie's in New York (Oct. 3-7, 25-29 and Nov. 1-7); at the Odon Gallery in Toronto (Oct. 17-20), and at Christie's London (Nov. 17-26).

Waterhouse, considered a late pre-Raphaelite by art historians, took the painting's title from the 17th-century Robert Herrick poem, To the Virgins,to make much of time. Based on the Greek myth of Persephone, goddess of springtime and, after her abduction by Hades, Queen of the Underworld, it depicts two nymphs picking flowers, watched by two companions in the distance.

Wagner says he has sold paintings as expensive as the Waterhouse before, but nothing as important as this "once-in-a-lifetime" work. But for a true art dealer, he insists, the selling is anti-climactic. "The getting is the thing."