Mary had seen the advertisement for the Personal Elf-sistant too many times to count. It started in November, on the bus, when she was on the way to work. On a big poster across the aisle from where she sat, a famous actress in golden pearls held a foot-tall, cerulean, beaming elf. Elf! The best friend you knew you never had. At the time, Mary had scoffed. Who wanted to tote around an elf all day, for God’s sake? she thought. It sounded worse than a dog. Mary didn’t know anything about elf-care.

But then the poster started popping up everywhere Mary went. A printed leaflet appeared in every mailbox on her street one Thursday. The dentist stuck it to the ceiling so patients could stare at it while they lay back in the chair, their mouths stretched into perpetual yawns. There was even a massive, blown-up version plastered on the building opposite her office; she could see it clearly from her desk. Mary would catch herself staring at it blindly, mindlessly, for minutes at a time. When she broke out of the trance, she couldn’t quite remember what she had been thinking about.

In a few weeks, Mary didn’t find the elf so silly anymore. Now when she thought about the elf, she felt a strange combination of euphoria and undirected but palpable jealousy. By this time, the poster had imprinted itself in her memory, and she could easily draw to mind the woman’s glorious smile and pearls, the elf’s lovely blue hue. The tagline started to thread its way through her thoughts more and more often. She did feel like she was missing a best friend. She was feeling particularly lonely these days.

The box arrived on her doorstep three days after she ordered it. Mary read the instructions and nervously opened the package. The elf popped to life, eager and grinning, just like the adverts. The two new friends introduced themselves and the elf asked Mary a few questions to get to know her better. After reciting her gender, date of birth, bank account number, social security information, a list of her closest friends (ranked by how much she liked them), all of her previous boyfriends and why they broke up (only two, one because he slept with the prom queen, the other because he moved to Iowa), her personal and family medical history (depression, high blood pressure, heavy periods), her key interests and dislikes (novels about nature, beauty creams, avant-garde pet portraits, criminal justice, DIY flower pots, space), and all the purchases she had made in the last one, seven, and thirty days, Mary was feeling pretty excited. The elf was going to know her back to front.

That was the idea. The elf told Mary about a special deal on pork chops at her favorite diner. Mary was delighted to head out on the town escorted by her shiny new friend. She placed the elf on her shoulder, where it could be seen and envied by everyone, while whispering continually in Mary’s ear. By the time they got off the bus, Mary had learned that dry skin was one of the leading causes of skin cancer and that two stores downtown sold the same strand of enviously iridescent pearls on the actress’s throat. They decided to stop at the pharmacy and the department store on the way to the diner, and Mary quickly forgot what life was like before.