Will is the central character in The Navidson Record subplot of the novel.
A stint in the army early in his life leads him to a very successful career as a photographer, primarily in war-torn parts of the world; his role as an impartial documentarist of war affects him deeply.
Later in his life, he moves to the eponymous house (located in the southeastern Virginia countryside), in an effort to find "[a] place to drink lemonade and watch the sun set", a place to "once and for all stay in and explore the quieter side of life" (page 9).
However, the unnatural events that occur thereafter have a profound effect upon him and his relationship with his partner, Karen.
Karen Green
Karen is Will's partner and a former fashion model.
She suffers from claustrophobia, and throughout the novel refuses to enter the labyrinth within her house.
She also seems to be extremely insecure regarding her relationship with Will; he is 'her rock,' though it is confirmed that she had at least three long-term affairs during the course of their relationship. Curiously, the events of the novel only seem to reduce her dependence on Will (as well as contributing to the eventual dissolution of their relationship).
It is speculated that, during Karen's childhood, her stepfather once took Karen and her sister into a barn in their backyard, putting one sister in a well while he raped the other, and vice versa. This event is widely considered to be the cause of her claustrophobia. However, several footnotes and comments about the incident question this claim (another of many examples of the use of an unreliable narrator in the novel).
In the aftermath of the events in the house, she becomes an unlikely editor, approaching many real characters (including Stephen King, Stanley Kubrick, Hunter S. Thompson, Douglas Hofstadter, Harold Bloom, and Jacques Derrida) for comment on The Navidson Record, albeit comment within the fictional universe of the novel.
Eventually, she is reunited with Navidson after she conquers her claustrophobia and saves him from the abyss of the labyrinth.
Tom is Will Navidson's somewhat estranged twin brother;
Tom is a carpenter with substance addiction problems, who is markedly less successful than Will in his personal and professional life.
After approximately 8 years of little contact, Will contacts Tom when he notices that his house is larger on the inside than the outside.
A section of the novel, called "Tom's Story", is a partial transcript of documentary evidence and radio communication with the outside world during his vigil within the labyrinth, which he spends alone with his radio, waiting for Will. This section is referred to in the book as a "sometimes funny, sometimes bizarre history of thoughts passing away in the atrocity of that darkness" (page 252).
He often refers to "Mr. Monster" and many of the jokes and anecdotes he provides are religious in nature. However, in a test of his true character, he bravely saves Will's children from being swallowed by the house before being swallowed himself.
Billy Reston
Billy is an engineer and a friend of Will's, whom Will enlists early on in the story to help him try to find a rational explanation for the house's oddities.
Billy uses a wheelchair, having been paralyzed from the waist down in a freak engineering accident in India; Will happened to be on the scene and took a photo of Billy moments before he became paralyzed. Billy came across the photo after his accident and kept it as a reminder that he was fortunate to have survived.
Once the house's irregularities become more extreme, Billy joins Will and Tom in a thorough analysis; after Holloway and his men go missing, Billy insists on joining Will on the rescue mission, navigating the maze in his wheelchair.
He eventually saves Will and Holloway's men from Holloway by engaging in a firefight with him, holding him back long enough for the house to "consume" Holloway.
Billy survives the journey into the maze, but suffers persistent cold spells afterward as well as sustaining damage to his wheelchair.
Holloway Roberts
Holloway is an experienced explorer whom Will contacts in an effort to properly explore the labyrinth beneath his house.
Holloway is presented as the consummate outdoorsman: He has successfully engaged in numerous expeditions which would have killed normal men, and is an expert in all forms of survivalist equipment, from spelunking gear to firearms.
He engages in two brief explorations of the labyrinth before deciding to take his men on a third, prolonged expedition, prior to which they load themselves up with enough food and water to last several days and enough provisions to—they believe—safely guide them back home. During the course of this exploration, Holloway reaches the bottom of the Great Staircase and becomes deranged due to finding nothing but more empty hallways.
The house's bizarre architecture leads him to believe an image he sees down a hall is the "monster" stalking them when, in fact, he is actually looking at his own men; he shoots one of them, and, upon realizing what he has done, suffers a complete psychological breakdown and tries to murder them. Eventually, the house "traps" him by sealing him inside a series of locked chambers; alone and insane, Holloway records a series of unsettling final messages on a video camera before filming himself committing suicide.
The tape of his death is recovered by Will from the labyrinth. The seconds leading up to the end of the tape reveal that either 1) Holloway's corpse is devoured by the "monster" he is convinced is real or 2) Holloway merely disappears into the blackness of the house.
When the House begins to attempt to harm the others late in the novel, Reston calls out Holloway's name. Whether Holloway had some influence on the house's actions (before or after his suicide) is left ambiguous.
Kirby 'Wax' Hook: Another explorer of the labyrinth in Navidson's house. He is ultimately shot in the shoulder by Holloway, but he survives. The House leaves him with limited functionality in that shoulder, and an inexplicable case of impotence. However, after Navidson reenters the House for a fifth and final exploration, these symptoms disappear. Wax has a reputation as a flirt, who constantly attempts to hook up with women. He kisses Karen Green, a scene which Will later witnesses on camera.
Jed Leeder: The third explorer of the labyrinth in Navidson's house. He is shot by Holloway in the jaw, killing him.
Chad Navidson: Will Navidson and Karen Green's son, the older sibling. Around the times of the explorations, Chad is described as becoming increasingly aggressive and wandering.
Daisy Navidson: Will Navidson and Karen Green's daughter. During the explorations of the house, Daisy is described as suffering from echolalia.
