Her imagination?
No, the sound was unmistakable.
"I do hear it," Rhyme said.
"It's coming from downstairs, the basement."
A regular beat. Not like a human sound.
A timed detonator? she wondered. And thought again about a booby trap. The perp was smart. He'd know that a crime scene team would spare no effort to search the substation. He'd want to stop them. She shared these thoughts with Rhyme.
He replied, "But if he'd put together a trap why hadn't he done it near the wire?"
They came to the same conclusion simultaneously but he voiced the thought: "Because there's some greater threat to him in the basement." Rhyme then pointed out, "If the power's off what's making the noise?"
"It doesn't sound like one-second intervals, Rhyme. It might not be a timer." She was gazing over the railing, careful not to touch the metal.
He said, "It's dark, I can't see much."
"I'm going to find out." And then she started down the spiral staircase.
The metal staircase.
Ten feet, fifteen, twenty. Random shafts of light from the halogens hit portions of the walls down here, but only the upper portions. Below that everything was murky, the smoke residue thick. Her breaths were shallow and she struggled not to choke. As she approached the bottom, two full stories below the main floor, it was hard to see anything; the miner's light reflected back into her eyes. Still, it was the only illumination she had; she swung her head, with the light, from side to side, taking in the myriad boxes and machinery and wires and panels covering the walls.
She hesitated, tapped her weapon. And stepped off the bottom of the stairs.
And gasped as a jolt pierced her body.
"Sachs! What?"
Sachs had missed the fact that the floor was covered in two feet of freezing brackish water. She couldn't see it with the smoke.
"Water, Rhyme. I wasn't expecting it. And look." She focused ten feet or so over her head at a pipe that was leaking.
That was the sound. Not a click, but dripping water. The idea of water in an electrical substation was so incongruous--and so dangerous--that it hadn't occurred to her that this could be the source of the noise.
"Because of the blast?"
"No. He drilled a hole, Rhyme. I can see it. Two holes. Water's also flowing down the wall--that's what's filling up the room."
Wasn't water as good an electrical conductor as metal? Sachs wondered.
And she was standing in a pool of it, right next to an array of wires and switches and connections above a sign: DANGER: 138,000 VOLTS
Rhyme's voice startled her. "He's flooding the basement to destroy evidence."
"Right."
"Sachs, what's that? I can't see it clearly. That box. The big one. Look to the right. . . . Yes, there. What is it?"
Ah, finally.
"It's the battery, Rhyme. The backup battery."
"Is it charged?"
"They said it was. But I don't . . ."