Five women pick up their backpacks and start walking along a muddy track. Only four come out on the other side. The hike through the rugged Giralang Ranges is meant to take the office colleagues out of their air-conditioned comfort zone. At least that's what the corporate retreat website advertises. Federal Police Agent Aaron Falk has a particularly keen interest in the whereabouts of the missing bushwalker. Alice Russell is the whistleblower in his latest case – and Alice knew secrets. Far from the hike encouraging teamwork, the women tell Falk a tale of suspicion, violence and disintegrating trust. And as he delves into the disappearance, it seems some dangers may run far deeper than anyone knew.