the Luminol reacted with oxidized metals in the stone, producing pinpoints of luminescence. Gary sprayed a fresh arc across the wall, and a new swath of stars appeared, eclipsed by his shadowy outline as he moved past. There was a loud thump, and the silhouette suddenly lurched forward.
“Shit.”
“You okay, Gary?” said Yates.
“Hit my shin against something. The stairs, I think. Can’t see a goddamn thing in this…” He stopped. Then murmured: “Hey, guys. Look at this.”
As he moved aside, a patch of blue-green floated into view, like a ghostly pool of ectoplasm.
“What the hell is that?” said Corso.
“Light!” called Pete.
Maura turned on the lamp. The blue-green pool vanished. In its place she saw only the wooden staircase leading up to the kitchen.
“It was on that step there,” said Gary. “When I tripped, it caught some of the spray.”
“Let me reposition this camera. Then I want you to move up to the top of those stairs. Think you can feel your way down if we turn off the lights?”
“I don’t know. If I go slowly enough-”
“Spray the steps as you come down.”
“No. No, I think I’m gonna start from the bottom and go up. I don’t like the idea of backing down the stairs in the dark.”
“Whatever you’re comfortable with.” The camera flash went off. “Okay, Gary. I’ve got my baseline. Whenever you’re ready.”
“Yeah. You can hit the light, Doc.”
Maura turned off the lamp.
Once again, they heard the hiss of the spray bottle dispersing its fine mist of Luminol. Near the ground, a splash of blue-green appeared, then above it another splash, like ghostly pools of water. They could hear Gary’s heavy breathing through his mask, and the creak of the steps as he backed up the stairs, spraying the whole time. Step after step lit up, forming an intensely luminous cascade.
There was nothing else that this could be, she thought. It was smeared across every step, trickles of it streaking down the sides of the staircase.
“Jesus,” murmured Gary. “It’s even brighter up here, on the top step. Looks like it came from the kitchen. Seeped under the door and dripped down the stairs.”
“Everyone stay right where you are. I’m taking the shot. Forty-five seconds.”
“It might be dark enough outside now,” said Corso. “We can start on the rest of the house.”
Rizzoli was waiting for them in the kitchen as they came up the stairs, hauling their equipment. “Sounds like it was quite a light show,” she said.
“I think we’re about to see even more,” said Maura.
“Where do you want to start spraying now?” Pete asked Corso.
“Right here. The floor nearest the cellar door.”
This time, Rizzoli did not leave the room when the lights went off. She backed off and watched from a distance as the mist of Luminol was sprayed across the floor. A geometric pattern suddenly glowed at their feet, a blue-green checkerboard of old blood trapped in the linoleum’s repeating pattern. The checkerboard grew like blue fire spreading across a landscape. Now it streaked up one vertical surface, into broad swipes and smears, into arcs of bright droplets.
“Turn on the lights,” said Yates, and Corso flipped the switch.
The smears vanished. They stared at the kitchen wall, which no longer glowed blue. At worn linoleum with its repeating pattern of black and white squares. They saw no horror here, just a room with yellowed flooring and tired appliances. Yet everywhere they had looked, only a moment ago, they had seen blood screaming at them.
Maura stared at the wall, the image of what she’d seen there still burned in her memory. “That was arterial spray,” she said softly. “This is the room where it happened. This is where they died.”
“But you saw blood in the cellar as well,” said Rizzoli.
“On the steps.”
“Okay. So we know at least one victim is killed in this room, since there’s arterial spray on that wall there.” Rizzoli paced across the kitchen, unruly curls hiding her eyes as she focused on the floor. She stopped. “How do we know there aren’t other victims? How do we know this blood is from the Sadlers?”
“We don’t.”
Rizzoli crossed to the cellar and opened the door. There she stood for a moment, gazing down the dark stairway. She turned and looked at Maura. “That cellar has a dirt floor.”
A moment passed in silence.
Gary said, “We have GPR gear in the van. We used it two days ago, on a farm out in Machias.”
“Bring it into the house,” said Rizzoli. “Let’s take a look at what’s under that dirt.”
TWENTY-TWO
GPR, OR GROUND-PENETRATING RADAR, uses electromagnetic waves to probe beneath the ground’s surface. The SIR System-2 machine that the techs unloaded from the van had two antennae, one to send out a pulse of high frequency electromagnetic energy into the ground, the other to measure the echoing waves bounced back by subsurface features. A computer screen would display the data, showing the various strata as a series of horizontal layers. As the techs carried the equipment down the steps, Yates and Corso marked off one-meter intervals on the cellar floor to form a search grid.
“With all this rain,” said Pete, unrolling electrical cable, “the soil’s going to be pretty damp.”
“Does that make a difference?” asked Maura.
“GPR response varies depending on the subsurface water content. You need to adjust the EM frequency to account for it.”
“Two hundred megahertz?” asked Gary.
“It’s where I’d start. You don’t want to go any higher, or we’ll get too much detail.” Pete connected cables to the backpack console and powered up the laptop. “That’s going to be something of a problem out here, especially with all these woods around us.”
“What do the trees have to do with it?” Rizzoli asked.
“This house is built on a wood lot. There’s probably a number of cavities under here, left over from decayed roots. That’s going to confuse the picture.”
Gary said, “Help me get on this backpack.”
“How’s that? You need to adjust the straps?”
“No, they feel fine.” Gary took a breath and looked around the cellar. “I’ll start at that end.”
As Gary moved the GPR across the earthen floor, the subsurface profile appeared on the laptop screen in undulating stripes. Maura’s medical training had made her familiar with ultrasounds and CT scans of the human body, but she had no idea how to interpret these ripples on the screen.
“What are you seeing?” she asked Gary.
“These dark areas here are positive radar echoes. Negative echoes show up as white. We’re looking for anything anomalous. A hyperbolic reflection, for example.”
“What’s that?” said Rizzoli.
“It’ll look like a bulge, pushing up these various layers. Caused by something buried underground, scattering the radar waves in all directions.” He stopped, studying the screen. “Okay, here, see this? We’ve got something about three meters deep that’s giving off a hyperbolic reflection.”
“What do you think?” asked Yates.
“Could be just a tree root. Let’s mark it and keep going.”
