Some places keep their secrets underground.

Bestselling author Joyce Deborah Collins has returned to Richmond to watch her strangest novel become a film.

Her story centres on Queen Charlotte's Cottage in Kew Gardens and an impossible proposition: that somewhere within its apparently innocent walls lies a doorway through time. Step through it and you might find another century.

You might even find the person you were always meant to meet.

Director, actor and producer Tom Sangnier, owner of the Kew Gardens Hotel, intends to put Joyce's extraordinary story on screen.

But while everyone is looking backwards through time, something much more frightening is happening in the present.

A child has disappeared.

Then girls begin vanishing around Kew Gardens and Isabella Plantation.

Bodies are found.

A murder at Sangnier's hotel turns a film set into a crime scene. And when Joyce herself is killed, suspicion falls upon the man who was bringing her impossible story to life.

Into the investigation comes Christine Joanna Hart, psychotherapist and former private investigator, carrying her own history of investigating serial killers and cases in which the official explanation never quite accounted for everything.

What begins as a murder investigation leads towards old crimes, secret operations, rumours of anomalous activity and something hidden beneath one of London's most beautiful landscapes.

Because perhaps Joyce Collins chose the wrong mystery.

Perhaps the question was never what lies through the cottage.

Perhaps it was what lies beneath it.