The Mephisto Club

at the first killing, represented an element of Udjat.”
    Jane frowned at Oliver’s sketches, at the numbers he had jotted in the various sections of the all-seeing eye. “You’re saying that the circle at the first killing is really supposed to be the iris.”
    “Yes. And it has a value.”
    “You mean it represents a number? A fraction.” She looked up at Oliver and saw that he was leaning toward her, a flush of excitement in his cheeks.
    “Exactly,” he said. “And that fraction would be?”
    “One fourth,” she said.
    “Right.” He smiled.
“Right.”
    “One fourth of what?” asked Frost.
    “Oh, that we don’t know yet. It could mean a quarter moon. Or one of the four seasons.”
    “Or it could mean he’s completed only a quarter of his task,” said Edwina.
    “Yes,” said Oliver. “Maybe he’s telling us there are more kills to come. That he’s planning a total of four.”
    Jane looked at Frost. “There were four place settings at the dining table.”
    In the pause that followed, the ringing of Jane’s cell phone sounded startlingly loud. She recognized the number for the crime-scene lab and answered it at once.
    “Rizzoli.”
    “Hi, Detective. It’s Erin in Trace Evidence. You know that red circle that was drawn on the kitchen floor?”
    “Yeah. We’re talking about it right now.”
    “I’ve compared that pigment with the symbols from the Beacon Hill crime scene. The drawings on the door. The pigments do match.”
    “So our perp used the same red chalk at both scenes.”
    “Well, that’s why I’m calling. It’s not red chalk.”
    “What is it?”
    “It’s something a lot more interesting.”

SIXTEEN
    The crime lab was in the south wing of Boston PD’s Schroeder Plaza, right down the hallway from the homicide unit offices. The walk took Jane and Frost past windows that looked out over the tired and broken neighborhood of Roxbury. Today, under a cloak of snow, all was purified and white; even the sky had been cleansed, the air crystalline. But that sparkling view of skyline drew only a glance from Jane; her focus was on Room S269, the trace evidence lab.
    Criminalist Erin Volchko was waiting for them. As soon as Jane and Frost walked into the room, she swiveled around from the microscope that she’d been hunched over and swept up a file that was sitting on the countertop. “You two owe me a stiff drink,” she said, “after all the work I put into this one.”
    “You always say that,” said Frost.
    “This time I mean it. Out of all the trace evidence that came in from that first scene, I thought this would be the one we’d have the least trouble with. Instead, I had to chase all over the place to find out what that circle was drawn with.”
    “And it’s not plain old chalk,” said Jane.
    “Nope.” Erin handed her the folder. “Take a look.”
    Jane opened the file. On top was a photographic sheet with a series of images. Red blobs on a blurred background.
    “I started with high-magnification light microscopy,” said Erin. “About 600X to 1000X. Those blobs you see there are pigment particles, collected from the red circle drawn on the kitchen floor.”
    “So what does this mean?”
    “A few things. You can see there are varying degrees of color. The particles aren’t uniform. The refractive index also varied, from 2.5 to 3.01, and many of those particles are birefringent.”
    “Meaning?”
    “Those are anhydrous iron oxide particles. A quite common substance found around the world. It’s what gives clay its distinctive hues. It’s used in artists’ pigments to produce the colors red, yellow, and brown.”
    “That doesn’t sound like anything special.”
    “That’s what I thought, until I dug deeper into the subject. I assumed it came from a piece of chalk or a pastel crayon, so I ran comparisons against samples we obtained from two local artists’ supply stores.”
    “Any matches?”
    “None. The difference was immediately apparent under the microscope. First, the red pigment granules in the pastel crayons showed far less variability in color and refractive index. That’s because most anhydrous iron oxide used in pigments today is synthetic—manufactured, not mined from the earth. They commonly use a compound called Mars Red, a mixture of iron and aluminum oxides.”
    “So these pigment granules here, in this photo, aren’t synthetic?”
    “No, this is naturally occurring anhydrous iron oxide. It’s also called hematite, derived