When the bones of a teenage boy are discovered on Mount Wingen, Detective Rebecca Giles dives deep into a missing persons case that has haunted her rural town for twenty years . . .

Five went up. Only four came down . . .

In April 2006, fifteen-year-old Oliver went hiking to the lookout on Burning Mountain - and vanished without trace.

His schoolfriends - Bob, Bell, Phil and Paul - were the last ones to see him on the trek, yet the teenagers were never able to explain his disappearance.

Almost twenty years later, Detective Rebecca Giles is called to bushland on nearby Mount Wingen. There a skull has been dug up, reviving the mystery that has haunted the Upper Hunter area for years.

Giles is convinced that they have finally found the missing boy, and that his four friends - all now in their mid-thirties - have always known much more than they revealed. In particular, about the argument that caused Oliver to head down the mountain on his own.

But when she discusses the case with her father, retired Superintendent Benjamin Giles, another suspect is thrown into the mix. One that for Giles is uncomfortably close to home . . .