Once I returned to work, I pretended to no longer hear the hum. It was a convincing performance. Paul let me sleep in our bed again, like a dog being let back into the house if it didn’t piss on the carpet. Ashley stuck her tongue out at me at her games and poked my bum as I passed her in the halls. I got through my lessons, cracked jokes in the staff lounge, and colleagues resumed sharing the minutiae of their marital dysfunction with me. In other words, things were back on track.

Fast-forward two weeks. About forty-five minutes after the final school bell of the day one evening, I locked my classroom door, walked through the halls nodding goodbye to the cleaning staff, and stepped out into the staff parking lot, which was all but empty. The yellow school buses were gone. A few kids were still waiting across the street for the city bus, smoking. I got into my silver Toyota, drove three blocks, rounded the corner, and pulled over beside a small, shady park. The park was connected, by way of an overgrown path, and the adjacent elementary school’s playground, to the back field of the high school. I pretended to be looking for something in the glove compartment so as not to seem suspicious, even though there was no one around. After about five minutes, Kyle appeared in the small park with his hood pulled up, crossed to my car, and climbed into the passenger seat. We drove without talking for a few moments, scanning the nearby streets, before he took off his hood, and we eased into our usual dynamic.

Kyle and I had started meeting up after class. At first, it was just to talk and share experiences. And then, we began to share theories. Neither of us was prepared to believe the sound was in our heads. We figured there must be a source, and if there was a source, then it must be possible to find it. We compared articles we found online, combed through comment threads, and drafted up a list of possible culprits, which we plotted on a map of the neighbourhood—nine computer pages of Google Maps satellite views that we printed out, taped together, and laminated. Before long one thing became abundantly clear—if we wanted to track down the source, we would have to leave the classroom.