The location of the Zeiss SEM was enthroned within a windowless room of teal and beige wall cupboards and shelves, counter space, and sinks. Because the extremely expensive instrument was very sensitive to mechanical vibration, magnetic fields, and electrical and thermal disturbances, the environment was precisely controlled.

The ventilation and air conditioning system were independent of the rest of the building, and photographically safe lighting was supplied by filament lamps that did not cause electrical interference and were directed up at the ceiling to dimly illuminate the room by reflection. Floors and walls were thick steel-beamed reinforced concrete impervious to human bustling or the traffic of the expressway.

Mary Chan was petite and fair-skinned, a first-rate microscopist, this minute on the phone and surrounded by her complex apparatus. With its instrument panels, power units, electron gun and optical column, X-ray analyzer, and vacuum chamber attached to a cylinder of nitrogen, the SEM looked like a console for the space shuttle. Chan’s lab coat was buttoned to her chin, and her friendly gesture told me she would be but a minute.

“Take her temperature again and try the tapioca. If she doesn’t keep that down, call me back, okay?” Chan was saying to someone. “I’ve got to go now.”

“My daughter,” she said to me as an apology. “A stomach upset, most likely from too much ice cream last night. She got into the Chunky Monkey when I wasn’t looking.”

Her smile was brave but tired, and I suspected she had been up most of the night.

“Man, I love that stuff,” Marino said as he handed her our packaged evidence.

“Another metal shaving,” I explained to her. “I hate to spring this on you, Mary, but if you could look at it now. It’s urgent.”

“Another case or the same one?”

“The fire in Lehigh County, Pennsylvania,” I replied.

“No kidding?” She looked surprised as she slit taped brown paper with a scalpel. “Lord,” she said, “that one sounds pretty awful, based on what I heard on the news, anyway. Then the FBI guy, too. Weird, weird, weird.”

She had no reason to know about my relationship with Benton.

“Between those cases and the one in Warrenton, you have to wonder if there isn’t some whacko pyro on the loose,” she went on.

“That’s what we’re trying to find out,” I said.