“His children are far from safety;They shall be crushed at the gatewithout a rescuer.” Job 5:4

A man, Cutter, parks his automobile near a home with a “For Sale” sign on the front lawn. After speaking briefly with a Realtor, Cutter signs his name in a guest book and makes his way through the house, where he takes particular interest in a little girl’s bedroom. Later that evening, the owners return home and tuck their young daughter, Patricia, into bed. Later that night, Patricia suddenly begins screaming.

An alarm company security guard discovers the parent’s bludgeoned bodies on the first floor of the house. But Patricia’s whereabouts are unknown. Frank, Bletcher and a team of detectives search the home for clues. After examining the alarm system, which was triggered when the intruder left the home–but not when he entered–Frank realizes the killer attended the open house and then hid somewhere until the family returned home. As he takes in the crimes scene, Frank is drawn towards an air heater vent. He yanks the grill from the wall, revealing Patricia, her small body stuffed inside the small space, curled into a ball and catatonic with fear.

Patricia is rushed to a nearby hospital where she is treated for dehydration and extreme shock. Catherine cautions the detectives that, although Patricia is the only eyewitness to the murders, her psychological state is extremely delicate. Catherine asks that the police postpone their interview, not wanting to force Patricia to relive the terrifying ordeal.

Meanwhile, Frank, Bletcher and Giebelhouse enlist the services of a handwriting expert and examine the killer’s signature (written in the guest sign-in book as “John Allworth”). Graphological analysis links the perpetrator’s signature to a least thirty-seven open house registers over the previous six months. Frank believes the key to catching the culprit lies in finding a pattern with the homes he visited.

When the killer mails a videotape of the murders to a Realtor, Frank is puzzled. The case develops yet another strange twist when the killer sneaks into an open house and murders a divorced woman by shooting her point blank with a shotgun. Bletcher notes the perpetrator called 911 and notified the police shortly after the murder. Frank notices a bloody red “X,” the same one which appeared to him in a vision, drawn beneath the welcome mat. Meanwhile, Patricia begins drawing “X’s” with her crayons.

While reviewing a videotape of the first murders, Frank spots the killer’s image in a reflection. He asks Catherine to show Patricia a photo of the killer, but suddenly, Frank retracts his request. He realizes that, all along, the killer wanted the police to approach Patricia and force her to relive the murder–in much the same way the killer has been reliving some unspeakable act his entire life.

Cutter, who works as a school crossing guard, plants the shotgun (used to commit the second murder) in a dumpster, and then notifies police of its whereabouts. The officer who takes the report from Cutter later sees the photograph from the video and identifies him.

Frank realizes that Cutter has been attempting to prove wrong our pretntions of safety–we are not as secure as we think we are. The police stake out a number of different open houses. Cutter visits the home where Frank and his colleagues have set up surveillance, but escapes into the neighborhood. Frank and Bletcher search the neighborhood and realize the killer is hiding inside a house nearby, where Frank discovers a couple tied up in their bed. Suddenly, Cutter steps from the shadows and strikes Frank with a curtain rod, knocking him to the floor. Before Cutter can finish his assault, the family dog charges and leaps at Cutter, knocking him over the a bannister and sending him crashing into a glass table on the floor below.