Inquiring minds want to know. With the Knocknaree woods being the site of ancient rituals (there's even a sacrificial altar), rumors of the supernatural abound.
I thought of the old superstition that the soul lingers near the body for a few days, bewildered and unsure. (5.67)
Even Rob sometimes wonders about the supernatural, although he's not the type to take this train of thought too seriously.
"There's no evidence of any royal burials or dwelling places on the site, but we found Bronze Age religious artifacts all over the place—the altar stone, votive figurines, a gold offering cup, remains of animal sacrifices and some possible human ones. That used to be a major religious site, that hill." (6.68)
The woods have history and when anything has that much human history, people start to think there are ghosts and spirits and other creatures living there.
"The wine you spilled. […] A libation?" (6.73)
Mark takes the Knocknaree site very seriously, and his offering of red wine to the grounds treads a fine line between religion and belief in the supernatural.
There was something unnatural about them—the perfect parallels, the neat shallow arcs, a stark, implacable impossibility. (6.139)
No one can explain how Rob's t-shirt was cut. It doesn't seem like anything that could have been done by a person or a tree branch, though…
"All I'll say is that there's been something just a little off kilter about that place all along. […] Do you believe, my boy, that a place can have a will of its own—that it can rebel, so to speak, against human mismanagement?" (10.170)
And this is why the police always have to debunk supernatural rumors, because people like this guy, who is a journalist, believe that the place itself might be killing folks.
[Cassie] told me about a time when she was nine and convinced all the other local kids that a magic wolf lived in the hills near the village. (11.125)
This is something kids do: They pretend there are magical beasts around. But some kids actually believe it. Strangely, Rob and his friends never believed there was anything supernatural in the woods when they were kids. And interestingly, people seem to believe it more as adults.
Sandra says she never heard anything like it. Like an enormous bird flapping its wings, she said, only she's positive it was a voiced sound, a call. (12.70)
There are lots of strange supernatural details in the testimonies of the witnesses for the 1984 crime, and all of them are slightly different from others. Some hear laughter, while some hear animal noises, or voices.
The darkness in front of me was shifting, condensing. […] Somewhere across the clearing something breathed; something big. (14.102)
We're not sure if Rob is actually witnessing something supernatural here, or if he's caught in between his dream state and reality and all the witness testimony about something weird in the woods is getting into his subconscious.
"There kept being these, these noises outside, like something was scratching at the walls of the shed." (21.46)
Damien even suggests something supernatural in the present-day case, and what he saw—or heard, in this case—is different than anything else, like Sandra's bird noise or the laughter Jonathan heard.