February 18, 2008 -- A Harvard-educated Manhattan jet-setter has been pegged as the money-laundering mastermind behind a massive LSD drug ring run out of a Kansas missile silo, The Post has learned.

Stefan Wathne, a 39-year-old scion of New York's socially prominent Wathne apparel family, surrendered to federal agents Jan. 7 as he stepped off a plane at Newark Airport - after three years on the lam.

Wathne is accused in a 2005 federal indictment of laundering as much as $3 million through Russia between 1996 and 2000 for what authorities have described as the most prolific LSD operation in US history.

His arrest marks the latest chapter in a bizarre federal drug case that has unfolded over five years and featured a surreal cast of characters.

In addition to Wathne - an erstwhile financial planner and former American Ballet Theatre trustee - the case has included a prominent Harvard psychiatrist and a deputy director of a UCLA drug-study program.

In another strange twist, singers Sting and Paul Simon helped pay the legal bills for a witness in the case.

The drug ring was cracked in November 2002, when the US Drug Enforcement Agency descended on a decommissioned military silo outside Topeka, which had been converted to a lab capable of churning out massive amounts of LSD.

The drug, formally known as lysergic acid diethylamid and originally used to study personality disorders, is the most potent hallucinogen known. The government banned it in 1966.

The feds arrested the Princeton- and Harvard-educated head of the operation, William Leonard Pickard, a noted chemist who at the time was deputy director of UCLA's Drug Policy Analysis program.

Pickard and an accomplice, California computer specialist Clyde Apperson, were charged with conspiracy and possession to distribute after agents seized enough raw material to produce 16 million doses of LSD, with an estimated street value of as much as $160 million.

The arrests put Wathne on the DEA's radar.

A Reykjavik-born Icelandic national whose family later put down roots here, Wathne was introduced to Pickard through Dr. John Halpern, a leading psychedelic researcher from Harvard's prestigious McLean Hospital.

Halpern, records show, was paid $319,000 by Pickard from 1996 to 1999 - the same years Wathne is charged with laundering money for Pickard.

Testimony at Pickard's drug trial suggested that Halpern was paid for the Wathne introduction.

Wathne's alleged role in the LSD ring was to take drug money, cycle it through Russia and then send it back to Pickard, partly in the form of a "donation" to his UCLA research program, according to testimony at Pickard's trial.

After the silo bust, Halpern made a deal with the feds and ratted out his friends.

He also rolled on a one-time New Mexico business partner, Alfred Savinelli, from whom Pickard had bought chemicals and glassware to make LSD.

Savinelli, whose company, Native Scents, sells botanicals and oils, was called as a witness. He testified that part of his legal bill was paid by Sting and Paul Simon, whom he counted as friends.

The two entertainers have declined to comment on the case.

Pickard was convicted in 2003 and is serving multiple life sentences.

Wathne had by then vanished from the New York scene and was reportedly living in Russia. Indicted in San Francisco federal court, he was declared a fugitive by the DEA.

A smooth-talking bon vivant fond of Rolex watches and expensive foreign cars, Wathne was well-known in social circles from Manhattan to Moscow.

In addition to being an ABT trustee, he sat on the board of the American Russian Youth Orchestra, which counts Laura Bush as its honorary chairwoman.

Wathne's 60-something mother, Thorunn, and her sisters, Soffia, 51, and Berge, 59 - a photogenic trio nicknamed "the triplets" and known for dressing alike in couture outfits at social functions - are fixtures on Manhattan's charity and party circuit.

Avid sportswomen, the three women made a fortune with their luxury outdoor and equestrian-related apparel and accessory firm. They sold to Bergdorf Goodman and I. Magnin and had a namesake boutique on West 57th Street that boasted Venetian plaster walls, a fireplace with a hand-carved limestone mantel and chandeliers made of antlers.

The firm also produced high-end luggage for designer Ralph Lauren.

Stefan Wathne headed the Moscow Institute for Advanced Studies, a nonprofit group run out of the West 56th Street Manhattan headquarters of the Wathne sisters' apparel business. The charity was staffed by Wathne employees, tax records show.

Wathne - who also used the alias Gunner Stefan Moller - was arrested in New Delhi on Sept. 24, 2007. Authorities here were trying to extradite him from India when he voluntarily agreed to return to the United States.

His arrest has sparked a new round of headaches for his family.

The mega-wealthy Wathne women recently sold off an $8 million oceanfront home in Nantucket. In 2001, they shuttered the Manhattan boutique.

They still hold millions in property around the city and own homes in Rye, Westchester County, and in Key Largo, Fla., records show.

On Jan. 10, Wathne pleaded not guilty to the money-laundering charges.

He surrendered his passport and was freed on $5 million bond to the custody of the Wathne sisters. Part of the family's vast real-estate holdings - including six apartments on Central Park South - were put up as collateral.

If convicted, Wathne faces up to 20 years in the slammer.

An assistant for the Wathnes referred calls to a lawyer, who did not return calls.

Outside the family home in Rye, a chauffeur said Stefan Wathne isn't talking.