Hannah Upp had been missing for nearly two weeks when she was seen at the Apple Store in midtown Manhattan. Her friends, most of them her former classmates from Bryn Mawr, had posted a thousand flyers about her disappearance on signposts and at subway stations and bus stops. It was September, 2008, and Hannah, a middle-school teacher at Thurgood Marshall Academy, a public school in Harlem, hadn’t shown up for the first day of school. Her roommate had found her wallet, passport, MetroCard, and cell phone in her purse, on the floor of her bedroom. The News reported, “Teacher, 23, Disappears Into Thin Air.”

A detective asked Hannah’s mother, Barbara Bellus, to come to the Thirtieth Precinct, in Harlem, to view the Apple Store surveillance footage. Barbara watched a woman wearing a sports bra and running shorts, her brown hair pulled into a high ponytail, ascend the staircase in the store. A man stopped her and asked if she was the missing teacher in the news. Barbara said, “I could see her blow off what he was saying, and I knew instantly it was her—it was all her. She has this characteristic gesture. It’s, like, ‘Oh, no, no, don’t you worry. You know me, I’m fine.’ ” Another camera had captured Hannah using one of the store’s laptops to log in to her Gmail account. She looked at the screen for a second before walking away.

The sighting was celebrated by Hannah’s friends, many of whom were camping out at her apartment. They made maps of the city’s parks, splitting them into quadrants, and sent groups to look in the woods and on running paths and under benches.

According to the Myers-Briggs personality test, which Hannah often referenced, she was an E.N.F.P.: Extraverted Intuitive Feeling Perceiving, a personality type that describes exuberant idealists looking for deeper meaning and connection. Five of her friends used the same phrase when describing her: “She lights up the room.” A friend told the News reporter, “Everyone you talk to is going to say she is their closest friend. She has no barriers. She was raised to trust and care for everyone, and she did.”

Two days after Hannah was seen at the Apple Store, she was spotted at a Starbucks in SoHo. By the time the police arrived, she had walked out the back door. The police recorded sightings of her at five New York Sports Clubs, all of them near midtown, where the detective on the case presumed she had gone to shower. In an article about her disappearance, the Times wrote, “It was as if the city had simply opened wide and swallowed her whole.”

On September 16th, the twentieth day she’d been missing, the captain of a Staten Island ferry saw a woman’s body bobbing in the water near Robbins Reef, a rocky outcropping with a lighthouse south of the Statue of Liberty. Two deckhands steered a rescue boat toward the body, which was floating face down. “I honestly thought she was dead,” one of the men said. A deckhand lifted her ankles, and the other picked up her shoulders. She took a gasp of air and began crying.

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The woman was taken to Richmond University Medical Center, on Staten Island. For three weeks, her own biography had been inaccessible to her, but when the medical staff asked her questions she was suddenly able to tell them that her name was Hannah and to give them her mother’s phone number. Barbara arrived within an hour. (Hannah’s father was living in India, where he taught at a seminary; her brother, a Navy officer, was stationed in Japan.) Barbara said that Hannah looked “both sunburned and pale, like she’d been pulled behind a boat for three weeks.” The first thing she said was “Why am I wet?”

She was treated for hypothermia, dehydration, and a severe sunburn on the left side of her body, and her condition rapidly improved. Four friends came to the hospital that afternoon. Manuel Ramirez, her roommate, said, “She saw me and smiled and said something like ‘I hope they release me soon, because I have to set up my classroom.’ She clearly didn’t get that three weeks had passed.”