Test of Friendship
The overarching theme of the entire Lockwood series as well as this particular volume is the power of friendship. The three main characters work in tandem in their role as psychic investigators with each bringing their own unique individual gifts and abilities. The key to success lies in the integration of these strengths and weaknesses into a functioning team. This teamwork through friendship that has already been established in the previous entries in the series is put to the toughest test yet in this volume with the introduction of a new character. Making this test all the more dramatic is that the member is a girl, thus creating a sense of jealousy and paranoia in the narrator who has up to this point been the only girl working alongside two boys.
The Natural Supernatural
It is simply a given than ghosts and spectral entities exist in the world we otherwise recognize as our own in this series of books. The protagonists and antagonists are two competing psychic research agencies. The existence of ghosts needs no explanation to anybody within the story. What is more significant, thematically, is that the reader does not need to be convinced of the existence of the paranormal. The theme being explored across the breadth of the series, including this particular volume, is the ease with which the suspension of disbelief can be manipulated. Unlike many traditional ghost stories, there is no major character representing skepticism. It is simply taken for granted that such unlikely entities exist. By this point in the series, even something as completely bizarre as a talking skeleton with a particularly snarky personality does not require explication. The book is, in this manner, pursuing a theme strongly suggesting that human beings are more open to the possibility of the existence of ghosts than to other supernatural or otherworldly entities.
The Past
The ghosts in this story are not just spectral entities existing in the present. The book takes seriously the definition of a ghost as being the leftover spirit of a once-living human. The investigation into the spirits haunting the present very often becomes a story of the humanity of that spirit in the past. A theme underlying this paranormality is that the past always impacts the present. This theme extends beyond the ghostly characters to give the relationships between the human characters an added dimensionality. The past in the form of experiences and events and knowledge delineated in the previous books begins affecting not just the present of this book, but the unknown future to be explored in the following volume.
