Just months ago, she was studying the translucent flesh of squid bought at a fish market, in the hope of replicating their gleam in the giant, handcrafted model she was making for a special exhibit on bioluminescence at the American Museum of Natural History.


Her final model of the Vampire Squid, made of linen smeared with liquid plastic, was so lifelike that it was singled out in the museum’s quarterly magazine. A few pages later in the same issue is a photo of the meticulous model maker at a museum gala — Carlisle Champalimaud, looking like a starlet, beaming in a flame-colored floor length dress, her husband in a tuxedo by her side.


This week Ms. Champalimaud was found dead, covered in her blood, on a landing in a building on the Lower East Side where she was staying with a friend. The police initially thought she had been attacked, but the city’s medical examiner found that the injuries to her head had been sustained in an accidental tumble — the result, it may be, of a combination of high heels, a heavy bag and slippery stairs.


With her ready smile and glamorous looks, Ms. Champalimaud, 29, the daughter of a prominent former city official, was a natural fit with the society Web sites that featured photos of her snapped at galas, charity events and gallery openings. But her life had recently begun to unravel: just a few months after the museum gala, Ms. Champalimaud and her husband separated after less than a year of marriage, though each had professed hope they could work things out.


“It was a difficult period,” said her husband, Anthony Lindley Champalimaud, 34, who is a vice president of real estate development for a Malaysian conglomerate and was in England when he heard the news that his wife had died. “We were intensely engaged with one another, but just needing space. It was not obvious where it would end.”


The days leading up to her death had been particularly painful. She had attended a wedding in Washington, D.C., over the weekend, just a week after her first wedding anniversary.


Her father, James R. Brigham Jr., who was New York City’s budget director during the financial crisis in the late 1970s and is now the chairman of an investment bank based in St. Louis, said she had been distraught, and that he had traveled to New York that morning to help her cope. “She said it was a really difficult weekend,” he said. Blond and witty, Ms. Champalimaud, who studied studio art at the University of Mary Washington in Fredericksburg, Va., loved the outdoors. She was an avid rafter, went on dinosaur digs, and was delighted when she parlayed an internship at the Natural History Museum into paid freelance work, cataloging thousands of specimens of fossilized mammals and fabricating exotic creatures.


Not long after her first date with Mr. Champalimaud, a longtime family friend, she agreed, on the spur of the moment, to accompany him on a 10-month work deployment to a remote town in Japan. He proposed after they returned. They married last year at St. George’s, the seaside boarding school Mr. Champalimaud attended, in Newport, R.I. Three months ago, they separated.


The morning of her death she was staying at the Orchard Street apartment of a friend, John Madtes, an old college housemate. The reason, her father said, was that she had misplaced the keys to her own apartment.


Ms. Champalimaud had returned from the Washington wedding early that morning and had headed with Mr. Madtes to the Sixth Ward, a nearby bar, according to a patron who said he knew Mr. Madtes but declined to give his name. It is unclear whether alcohol played a role in her death; the results of toxicology tests will not be available for several weeks, Grace Brugess, a spokeswoman for the medical examiner’s office said.


On Monday morning Ms. Champalimaud was planning to meet her father for lunch. As he drove into the city from La Guardia Airport they talked by phone, first at 9:25 and then at 9:30, he said. Shortly afterward, her body was found by a 19-year-old neighbor, at the foot of the stairway. She was dressed entirely in white, with the contents of a large, clothing-stuffed weekend bag around her, according to interviews he gave NBC News and other outlets. Her father arrived just after the ambulance left the building.


“It’s just devastating, it’s so unspeakably difficult,” he said. “I’ve received 100 e-mails, and almost to a person everyone says I don’t know what to say. And I don’t either, in a way. It’s just devastating to lose such a beautiful creature.”