He opened the door, climbed into the cab, and took off his freshly polished reading glasses.

“I put the sample through the chemical spectrometer three separate times,” Mark said.

“What did you find in it?” I asked.

Mark flipped open the yellow folder and pointed at a block of black text printed along the top of the test sheet.

“Concentrated thallium sulfate,” Mark said.

“It’s an odorless, tasteless heavy metal compound found in industrial rat poisons and older chemical solvents.”

I rubbed my right thumb against my knuckle and watched warm air rise from the floor vents.