The back exit of the industrial testing lab smelled of vinegar and cold concrete.

Mark Vance stood under the buzzing halogen light with his silk cloth in his hand, polishing his reading glasses before he looked up at me.

“You called my house at five in the morning, Raymond,” Mark said.

I took the small glass sample vial out of my coat pocket and held it out under the bare bulb.

I’d wiped the grease off the side of my stainless steel travel thermos before pouring the dark liquid into the glass, but a faint yellowish ring still clung to the rubber stopper.

“It was poured out of my office thermos yesterday,” I said.