Cassi Whelan, aged 12, and her father, Mike, have recently moved into a repaired house in Avondale, on the edge of Christchurch’s Red Zone. Although only four when the earthquakes destroyed the city, Cassi’s memories still haunt her, affecting much of her life. She is an obsessive runner who worries incessantly about her weight; she also has a phobia about enclosed spaces, especially if there are raised shelves or hanging objects. The wide-open spaces of the cleared Red Zone suit her fine.
While out running on her first weekend, she meets Jim McLean, a retired reporter, who now spends much of his time fishing in the Avon river. He knows the neighbourhood well and gives her information about a broken-down house next to the Whelan’s place, one of a few houses in the area that are still vacant since being condemned after the February 2011 earthquake. It was owned by a Pandora Horton and is now locally known as the Haunted House. This began as a play on the name Horton but ends up having meaning because of strange happenings around the house and its garage. Some people even claim to have seen a ghost hanging out on the section late at night.
When Cassi investigates the property she finds a very large boy sitting on a pile of newspapers in an otherwise empty room. He is Quinn Fordson, a strange lad of Cassi’s age who lives on the other side of the Haunted House. Quinn shows Cassi a way to get into the undamaged garage, which he suggests might contain witches things such as bats and poisonous spiders. Cassi’s motivation to explore the garage is a recently opened can of cat food visible through a window. She has an interest in cats stretching back to a family pet that went missing after the 2010 earthquake.
Once inside the garage, Cassi doesn't find a cat, but she does find other creatures - ones that should never be kept in captivity. Thus begins a mystery-adventure that will challenge Cassi and Quinn more than the earthquakes that had previously shaped most aspects of their lives. On one side is Cassi, Quinn and Jim McLean; on the other are two criminals who have no thoughts for the well-being of anyone other than themselves.