It was not so long ago that the X-Files hunk David Duchovny moped to Movieline magazine, "I feel isolated and lonely. I'm not happy." Little did he know that that was going to change completely. Last Tuesday [May 6, 1997], under a veil of virtual secrecy, Duchovny vowed eternal love to Tйa Leoni, lanky star of NBC's The Naked Truth. "I couldn't be happier," the native New Yorker, 36, told PEOPLE afterward, still in a somewhat giddy mood. "I'm married. I'm in my hometown. And," he added, referring to the NBA playoff series between his beloved New York Knicks and the Miami Heat, "the Knicks in six!"

Their four-month relationship, furtive as an X-Files conspiracy, scarcely surfaced publicly. And even X-Files costar Gillian Anderson was in the dark about the wedding. "David and Tйa just wanted to keep this quiet," says a friend, "without the helicopters."

The plot went something like this: Duchovny, having just finished shooting the season finale of his hit Fox series in Vancouver, hopped on a plane last Saturday and flew to New York to join Leoni, 31, a fellow Manhattanite whose series had already wrapped in L.A.

Monday morning with him wearing a phony mustache that failed to fool much of anyone they popped into City Hall for their marriage license. The following evening, with the groom dressed in a beige Armani suit and the bride decked out in a pale pink floral gown by Lily et Cie, the couple exchanged self-penned vows during a 20-minute ceremony in the garden of the Grace Church School. (Duchovny attended the school through eighth grade, and his mother, Margaret, works as an administrator there.) "This was a place that had meaning to them," says school admissions director Zelda Warner. "It was pretty and private."

The only guests were a half dozen family members: Leoni's parents, Anthony Pantleoni, a corporate attorney, and wife Emily, a nutritionist, along with the bride's brother Tom, who runs an antiques mall in Ojai, Calif.; and Duchovny's mother (now divorced from his father, Amram, a playwright and retired publicist living in Paris), his sister Laurie, a teacher in Brooklyn, and brother Danny, a commercial director, who served as best man. A friend of Duchovny's sister, Episcopal minister Craig Townsend, presided at the ceremony.

The party moved on to a private room in Gascogne, a French restaurant, for a quiet, informal meal. Duchovny dined on filet of trout. Leoni ordered quail with a port wine sauce. Oddly, the cake proved tough to cut, even though the couple gripped the knife together. "What's inside this thing?" the groom joked. The couple then spent their wedding night at the small, upscale Lowell Hotel.

Leoni and Duchovny first met back in 1992, at the start of their careers. A 1982 Princeton graduate who majored in English, Duchovny, who would go on to date such actresses as Winona Ryder and Perrey Reeves, was starring in quirky independent movies such as Kalifornia. Putney School alum Leoni whose past loves include novelist John Irving's son Colin was starring in a doomed Fox series, Flying Blind. A Tonight Show producer introduced them, but friendship didn't evolve into romance until the beginning of this year, when they met up at the party of a mutual friend in L.A.