Tam sat up. Her too-big T-shirt read #GIRLSQUAD. Her eyes were watery blue and her face seemed weirdly flat, like everything except her nose and eyes were on the same level. “Well, it looks like mine,” she said. “And that means at some point she’s going to mess up and use mine. Which is disgusting.”

Ms. O’Neil turned away with an eye roll. Tam saw it, too, and her lip curled as she prepared to say more.

Then Ms. O’Neil held up her hand, warding off the attack. “Okay, okay, don’t worry, I’ll take care of it.”

“Disgusting,” Tam repeated.

“Come on, Margaret,” Ms. O’Neil murmured, and we retreated to the garage. She grabbed a roll of duct tape out of her desk drawer and started to write on it with a black marker.

Since it seemed like I might be here for a while, I decided to take a chance. “You can just write Margot,” I said.

“Oh, is that what people call you?” she asked. “Okay.”

She wrote Margo, ripped the tape off the roll, and wrapped it—along with a wayward strand of her own long, curly hair—around the handle of the toothbrush.

“Ta-da,” she said. “Now it is clearly your toothbrush.”

In my old life, I would have said, Oh, excuse me, there’s a t at the end of my name.

Maybe even, Oh, excuse me, you’ve attached a piece of your hair to this device I’m supposed to insert into my mouth.

But now? Nah.

She carried it out and held it up to Tam, like a flag waved in a parade, as we passed the TV room. Tam didn’t quite seem to process what she was seeing, but she didn’t get up and follow to air further grievances, so I figured it was fine.

And it was. It worked out well enough, in the sense that I never used any toothbrush but my own for the entirety of the six weeks I spent at Palmer House. Tam found several other reasons to despise me, but Tam despised everyone, so I didn’t dwell on it.

ON THE MORNING of the third day of the seventh week, I was in the bathroom, brushing, when Tam came in, grabbed a random towel off the rack, and began using it to dry her hair. She glared at me in the mirror.

“Hah,” I said, with the toothbrush between my teeth.

“Don’t hi me,” she said. “I’m exhausted, and it’s your fault.”

“Uh-kah,” I said.

“Can I just tell you how miserable it is to have you here?”

I spat into the sink. “Sure.”