Toolbox Murders
Daisy Rain goes to her apartment in the Lusman Arms, a former luxury hotel undergoing renovations, and is beaten to death with a hammer by a man wearing a balaclava. In another room, new tenants Nell and Steven Barrows, a teacher and a medical intern, are introduced to the amenities and a few of the residents by Byron, the building manager. As Steven works long hours, Nell is left alone most of the time, and befriends Julia Cunningham, a neighbor down the hall, and Chas Rooker, an elderly man who reveals some of the history of the structure, mentioning it was made by Jack Lusman, who disappeared mysteriously, and that builders died while working on it.
As days pass, the Lusman Arms are plagued by mysterious circumstance; strange noises are heard throughout it and coming from the intercoms, Nell finds a trinket containing human teeth in a wall, and Julia and another tenant vanish, having been killed (with a drill and a nail gun, respectively) by the ski masked murderer, who hides their bodies. While looking into Julia's disappearance, Nell speaks with Chas, who offers cryptic warnings about the nature of the building, and sneaks Nell a note reading "Look for her in Room 504". Nell takes the advice, and discovers that there is no Room 504, and that all the other floors lack apartments whose numbering should end with 4.
Nell goes to the Los Angeles Preservation Society, where an employee tells her that Jack Lusman was an occultist who associated with a society that tried to mix science and magic, and that the symbols (which Nell copies down on her arms) decorating the building are part of a spell. The blueprints for the Lusman Arms also reveal that there is a townhouse hidden within the structure, hence all the missing rooms. Nell returns home, and finds a hatch on the roof of the building that allows entrance into the townhouse, where she uncovers a room dedicated to the Golden Age of Hollywood, torture chambers, and dozens of corpses. The killer, who had just butchered another tenant and the handyman, appears, and removes his mask to reveal that he is a monster, which the credits refer to as "Coffin Baby".
A teenage resident discovers that the webcam he had been using to spy on Julia had recorded her death, prompting him to go to Steven, who finds Nell's notes about the building, and goes looking for her along with the boy, Byron, and the doorman. The men send the teen to get the police after they find a passageway into Coffin Baby's lair, which they enter. Coffin Baby kills Byron and the doorman, and gives chase to Nell and Steven, the former of whom theorizes that Coffin Baby needs death and the Lusman Arms to continue existing. The Barrows are found by Chas, who tries to lead them to safety, and murmurs that Coffin Baby came into the world when he clawed his way out of his dead and buried mother's womb.
Coffin Baby leaps out from under a pile of human remains, fatally throws Chas at a wall, and captures Nell, but she is saved by Steven, who bludgeons Coffin Baby, and knocks a shelf onto him. The authorities arrive, and take Steven to a hospital, and as Nell returns to her apartment, the police lift up the debris that fell on Coffin Baby, who has disappeared. Coffin Baby crashes through Nell's window and tries to kill her, but is disoriented by the runes she had earlier drawn on her arms, distracting him long enough for a pair of police officers to barge in, and shoot him out a window, causing him to be hanged by a cord Nell had wrapped around his neck. The officers check on Nell, then go to the window, only to find that Coffin Baby has once again vanished.
violence, horror, murder