The passenger beside me on the train removed his shirt and kept rubbing his sweaty, naked chest against my arm. I repeatedly asked him to give me room, but he just laughed. When I finally took matters into my own hands, his face turned crimson and he pleaded, “Please, stop! You can’t do this!”

I waited until he leaned into me again.
Then, without looking at him, I reached into my bag and pulled out the bottle of hand sanitizer I had been carrying since the station.
He smirked, probably expecting me to clean my hands.
Instead, I squeezed some onto my palm and rubbed it across the bare skin of my arm—the exact patch he kept pressing his sweaty chest against.
For a few seconds, nothing happened.
Then he shifted.
His eyes widened.
“What did you just do?”
I stared out the window.
He pulled away so quickly his shoulder slammed into the aisle seat.
The passengers nearby turned toward us.
His face went from annoyed to alarmed.
“Please! Don’t! You can’t do this to me!”
That was when I finally looked at him.
“You said there wasn’t enough room,” I replied. “So I made a boundary.”
He glanced at my arm, then at his chest.
A violet stain had appeared across his skin.
The sanitizer wasn’t ordinary.
Earlier that morning, I had used a harmless UV-reactive security dye at work, and a little had leaked onto the outside of the bottle.
Now every time he rubbed against me, he had transferred more of it onto himself.
Under normal light, the marks were faint.
But above our seats was an emergency inspection lamp.
I reached up and switched it on.
His chest lit up with glowing purple streaks.
So did the side of his arm.
And, unmistakably, so did several smeared fingerprints on my sleeve.
The carriage went silent.
Someone behind us laughed.
Another passenger said, “So he really was doing it on purpose.”
The man grabbed for his shirt, but his luggage was wedged overhead.
His hands shook.
“Turn that off.”
I didn’t.
The conductor appeared at the far end of the carriage, drawn by the commotion.
The man stopped pleading.
He stared past me toward the window.
Then all the color drained from his face.
Because reflected in the glass, behind the conductor, stood two uniformed officers.
And one of them was already holding up a photograph.
A photograph of him.
read the entire Part 3