A ghost is the disembodied spirit or soul of a dead person that returns to the mortal world. Ghosts appear (or seem to appear) in several episodes of Forever Knight. Their status is usually indicated by lighting: a strong blue or blue-white light is shone directly on the actor, washing out the natural colour of the skin.
Throughout the Forever Knight television series there are intimations of the existence of other aspects of the supernatural besides the existence of vampires. However, until Season Three, rational explanations of their ostensible appearance could be proffered, in some instances explicitly by Nick Knight's pathologist friend, Dr. Natalie Lambert. In Season Three, however, the supernatural became more overt.
In "Dead of Night", Nick Knight and his partner, Tracy Vetter, are in the midst of the investigation of a murder at a reputedly haunted building, Kessel House, when both of them—along with other mortal friends and colleagues—begin seeing the ghosts of people from their past who had died in unfortunate circumstances.Nick repeatedly sees (and eventually speaks with) his long dead wife, Alyssa von Linz, whom he had married in 1528. At that time, he tried and failed to bring her across so that they could live forever as vampires: he took too much of her blood, and she died. Although primarily interested in reconnecting with Nick, Alyssa's ghost repeatedly warns him to leave Kessel House. Her intimations of danger to him are borne out in the climax of the episode when ghosts of other victims also appear (though there is no indication that he recognizes them individually). Most of these additional ghosts are visually identifiable by blue illumination. However, as he flees downstairs to escape, he is pursued through the walls, with the ghosts' faces appearing as distortions in the surface.
In additional subplots, Natalie Lambert sees the ghost of her deceased grandmother, Nana Tash; Tracy Vetter sees the ghost of Susan Feldman, a childhood friend killed in a train accident; and Captain Reese sees the ghost of his brother Jordan, who died in Vietnam.
The ghosts are seen only by the individual to whom they wish to appear. Though implied in most scenes, this becomes explicit in a scene in the 96th Precinct police station in which Susan appears to Tracy: the ghost uses poltergeistic powers to shift objects around the squad room, but no one but Tracy sees anything untoward.On the surface, all the ghosts seem to be looking for some sort of closure in their former lives. Alyssa seeks assurance that Nick loved and still loves her, and killed her only by accident. Nana Tash wants to know why Natalie never visited her in hospital when she was dying. Susan wants to preserve her friendship with Tracy, enticing her into harm's way so that she may join her in death. (Jordan's appearance is brief; but, by analogy, one might infer some conflict between him and his brother Joe, perhaps over his service in the army.) However, particularly through the Nana Tash subplot, it is intimated that the motive force behind the appearance is probably not the will of the deceased but rather the guilt of the living. Thus, once Natalie has explained to her grandmother her resentment of being hit by her, and apologized for not visiting her in hospital, the elderly woman's ghost disappears. Nick's guilt for killing Alyssa is somewhat alleviated by the fact that he has finally been able to assure her that he had never intended her death. Tracy, who had been unable to free her friend when her foot was caught on the railway track, comes to accept that there was nothing that she, another child, could have done to save Susan from being killed by an oncoming train. A tentative suggestion is therefore made that perhaps these ghosts are really projections of guilt; and that the true magic seen in "Dead of Night" is rather the mystical powers of Kessel House itself. However, even when considering this explanation for someone else's sight of a ghost, none of the characters considers it adequate to explain their own experience.
After she took her own life, Erica, Nick's former lover in "Last Act", returned to him as a ghost. She never haunted him, only recalled their love and explained why she did what she did. She asked for his company in the beyond but he refused.
Nick believed that he was seeing a ghost following him while on a case but it was really Alexandra looking to kill him. In a flashback, Nick recalled a time in which he was falsely accused of murder by a local community. When he confronted his accuser he said he was a ghost and then killed him.