Those of us who work in academia tend to think of ourselves as the kind of people who subscribe to a certain standard of behavior. This makes us especially vulnerable to those in our midst who exploit that sense of camaraderie and trust. A University of California, Berkeley professor learned that lesson the hard way when, during her sabbatical in Paris, she rented out her home to a professor from another university who was spending some time in the Bay Area. Since he was a fellow academic, she did not bother to check his references or do any other kind of due diligence that she might have done for anyone else, and that was her mistake.

Her nightmare began when he stopped paying rent and her neighbors contacted her and said her that they had seen him moving her stuff into the garage. Alarmed, she came back with a police officer to see what was going on.

Elizabeth Abel walked up to the front door of her house for the first time in four months and rang the bell. She’d just flown halfway around the world to drop in, unannounced, on the man who’d taken over her home.

When he came to the door, Abel says, the man didn’t seem surprised to see her—or the police officer standing beside her. “Oh, hi,” he said.

Abel peered behind him into her living room, which was practically empty. Most of her furniture was gone: a dining table and four chairs, two easy chairs, an antique piece. Her books and rugs were nowhere to be seen. Even the artwork had been taken off the walls.

As Abel walked around the place she’d called home for three decades, she had the distinct feeling that her life had been erased. In the family room, a small sofa, a table, and a television had been removed. Out on the back deck, the wooden table and benches were missing. The bedrooms were emptied out, her mattresses crammed into the office. Closets were sealed with blue painter’s tape. She turned to the man, who had been renting her place for the past several months—without paying. “What is going on here?” she demanded. “What are you doing?”

It is a truly bizarre story, not least about what the owner found after she finally evicted him and moved back in.

Moving back into her house, though, wasn’t without incident. First of all, Abel had to move all her furniture back into her house from her office and basement, where Peritz had stored it. And when she went to put her pictures back on the walls, Abel realized she couldn’t figure out where exactly they’d previously hung: The nails had been removed, the holes had been spackled over, and the walls had been repainted. It turned out that he had a history of renting other people’s homes and leaving them in a mess.

This is not normal. There is clearly more to this than the desire to get housing without paying for it. It is not clear what motivates the strange behavior of this tenant, why he seems to have this compulsion to needlessly reconfigure and even wreck the places that he rents. He is not talking and neither are his friends and colleagues, and officials of the university where he works are not taking any action either.

I have been interested in the rise of the sharing economy where people use services like Airbnb to rent out their homes and rooms within them to strangers for short terms. I have never used such services but it must be generally a good experience since it has become so popular. But as this story indicates, you should not assume that someone will be a good tenant merely by virtue of the kind of work they do.