Magnesium Smoke
Magnesium smoke is a symbol of ghosts' manifestation. People with their naked eyes cannot see or touch ghosts. Lucy says, "A tall, slim figure stood there, silhouetted by the swirling flashlight beams and clouds of magnesium smoke." The intangibility of ghosts makes it hard for most physic investigators to know the source of their power. In addition, no physical weapon can harm the ghosts because of their intangibility. The symbol of magnesium smoke shows readers the difficulty physic investigators must overcome while trying to eliminate ghosts from the haunted residential areas.
Cobwebs
Cobwebs are a symbol of visitors. In the novel's context, the visitors are spirits such as ghosts. Lucy says, "The concentration of spiders—always a sign of Visitors—told me that. Ahead was a little room, chocked with a thousand cobwebs." One of the vital diets of ghosts is spiders. Therefore, the heavy presence of cobwebs in any particular area signifies the possible arrival of ghosts. In physic investigations, cobwebs are an important sign that ghosts haunt the area. However, Lucy says that identifying the exact location of the ghosts within the cobwebs requires a third eye, the skull.
The Third Eye
The skull symbolizes Lucy's third eye, leading her to the realms of higher consciousness. Throughout the novel, readers note that Lucy can listen to the communication of ghosts, which is a rare talent among physic investigators. However, Lucy draws her powers from the human skull she carries wherever she goes. Lucy says, "Inside, radiating a smoky greenish light was a large glass jar with a human skull clumped in its depths." The skull can see things that Lucy cannot see using her physical eyes. For instance, Lucy can hear ghosts speaking but cannot see them. Therefore, the skull helps Lucy locate the ghosts' exact location.
