Five women reluctantly pick up their backpacks and start walking along the muddy track. Only four come out the other side.The hike through the rugged Giralang Ranges is meant to take the office colleagues out of their air-conditioned comfort zone and teach resilience and team building. At least that is 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 - in just a matter of days she was to provide the documents that will bring down the company she works for.Falk discovers that far from the hike encouraging teamwork, the women tell a tale of suspicion, violence and disintegrating trust. But does it include murder?