(SPOILER ALERT ...)

This movie is about the hero's (Trevor's) need to extricate his soul from a demonic/satanic ritual. That is, after killing Faith, he aborts said ritual (by not killing himself), putting his soul in limbo. The mad scientist somehow finds this out and kidnaps him to find the book used for the ritual. The (incarnate) earthly and trapped parts of his soul wake up from the mad scientist's implantation surgery (which is supposed to allow the mad scientist to read Trevor's thoughts(?)) at almost the same time. (To see this, note that the earthly part wakes up from the implantation surgery just before the one nurse says that her shift is over, while the tormented half wakes up two or three seconds later, just after.) Further evidence that they awaken in parallel realities is that the residents and principals of the "House of Love" introduce themselves to Trevor the second times he awakens, whereas Trevor already knows them. Trevor's knocking on both sides of the trunk (later on) further illustrates this point.

Trevor must reunite his ripped, tormented soul. Unwilling to relieve this tension by letting Faith kill him--to complete the ritual--he follows his dreams/visions. He therefore gravitates to the trunk in the attic. The significance of the trunk is revealed in the magic attached to it, which is revealed in the implicit inability of the mad scientist and others, and the explicit inability of Douglas, to open it; the trunk is controlled by a force which allows only Trevor to use it. Inexorably, the pieces of his soul meet (on either side of the opening to the trunk) and unify. Trevor's torment, and the film, abruptly resolve. His painful dreams evaporate and he regains his earthly existence.