Weapon in hand, she followed the tracks into the woods, wading through the wet, knee-high snow. The overhead tree branches were bare, and she could feel the sun on her face and hair.
A quarter of a mile in, she found a large open space of recently overturned dirt. Darby looked around the woods and didn't see any additional tyre tracks. They ended here. She called Bill Jordan.
'I think I found the spot where Fletcher buried the body,' Darby said. She told Jordan about the excavator tracks and poked the ground with her boot. The dirt was loose. 'We're going to need shovels.'
'See you in twenty.'
Sticking out of the ground was an inch of white PVC pipe. In the slant of sunlight, Darby saw that the white tubing extended deep into the earth. Kneeling, she took out her flashlight.
A ruined eye stared back at her.
'Help me,' Walter Smith croaked. 'I can barely breathe.'
Darby backed away, stumbled, and fell against the cold ground.
'I'm sorry!' Walter's raw, terrified voice echoed up the pipe from his crudely made coffin. 'I don't want to die in here. PLEASE!'
Darby tried to get to her feet and stumbled again. She knelt on all fours, heart hammering as she gasped for air.
Malcolm Fletcher had cut a hole into the coffin and fitted it with a PVC pipe that ran up to the surface so Walter wouldn't suffocate. He could breathe until he died of starvation or insanity.
'I told Mr Hale I was sorry! I'm sorry! I'm sorry!'
Did Hale know Walter was buried here? Did he plan to come out to this spot and drop food down the pipe to prolong Walter's torture?
You wanted Walter to suffer, Malcolm Fletcher had said. When you think back to that moment inside the bathroom, you'll wish you'd pulled the trigger.
In her mind's eye Darby saw herself pressing the handgun's muzzle against Walter's head. The cold, alien voice that spoke to her inside the bathroom was speaking to her now: Block the pipe and let him suffocate to death.
'Please,' Walter screamed. 'Please don't leave me here, I'm sorry.'
Darby recalled the photograph of Emma Hale's body lying on the bank of the Charles, buried under snow, discovered by a dog. Judith Chen's body lay on the autopsy table, the woman's face picked apart by fish. Walter Smith killed both women and he was going to kill Hannah Givens before turning the gun on himself.
'Please get me out of here,' Walter cried. 'I'm so scared. I don't want to die here alone without Mary.'
Block the pipe and cut off his air. Let him suffer.
Walter Smith deserved to suffer. She wanted him to suffer.
Do it. Nobody will know.
The wind blew through the woods, shaking the branches. Darby scrambled back across the ground and looked down the pipe.
'Hang on,' she said, reaching for her cell phone. 'Help is on the way.'