Swamped

"Well, I wouldn't be surprised if someone around here were still hiding a mask, but there isn't much time to look," you mutter. "So you'll be better off asking the doctor for some of the swampleaf they've got here."

"Swampleaf?" Minnie asks. "What, do I put that over my mouth?"

"No, it's..." You're struggling here, because you're fairly sure the explanation running through your head is years away. Fortunately, the man in purple is able to pick up the explanation.

"It puts you to sleep," he explains. "But if you dilute it enough, it just slows down your body processes for a little while. In particular, you'll breathe slower and take in a lot less gas. You'd need someone to lead you around, though, tends to dull the senses a bit."

"No offense meant, Crow, but I don't like the thought of my senses being dulled around you."

"Yeah, don't think I would if I were in your position either. We could get a bottle of water and a scrap of leaf and save that for emergencies, but that wouldn't be as good as a proper mask."

"Then give me yours," she replies.

That seems like a bad idea, considering it's from a different time period. You should probably push her away from that thought.