Carlton Chase runs up to a pay phone on a nighttime street in Worcester, MA. "Pick up!" he barks into the recording answering machine. "Call him off, give me chance to explain," he begs, before a shadow appears behind him. Afraid, Chase runs off and dashes into a nearby police station. The officers on duty stare at him strangely when he cries "Help me! Somebody wants to kill me!" Chase reaches for the cop's gun, and the police tackle him, tossing him into an empty cell. Chase pleads for his safety, saying that "He can get me." Suddenly, Chase's head explodes and his blood splatters against the small window of the cell.

The next morning, Scully examines the x-ray and determines that Chase was shot through the top of his head. A small dent in the air vent louver above proves this, but no one in the station heard the gunshot. Scully and Doggett climb into the air duct, where a small bullet hole leads a beam of light to a tiny hole on the roof. After Doggett finds a scrap of fabric that muffled the gun, they determine that the shooter fired once through two floors to reach his target. Yet they can't figure out how someone could make such a lucky shot. The agents search Chase's real estate office. The walls are rife with bullet holes, but the shells on the floor do not match the ones that killed Chase. On his desk are a stack of invoices from AAA-1 Surekill Extermination.

Tammi Peyton arrives for work at AAA-1 Surekill Extermination and plays back the answering machine's messages. Chase's frantic phone call from the previous night plays and she quickly erases it. She notices Chase's photo on the front page of the newspaper reporting his death. Tammi reaches for a lock box and is interrupted by her boss, Dwight Cooper. He ignores her questions about Chase's murder. Dwight confronts his brother, Randall, about the previous night's events. Randall defends himself by saying that Chase had been stealing from Dwight. Dwight warns him to ask first before he does anything else. Later that night, Dwight enters the warehouse of two drug dealers and demands their money and drugs. He points his finger at one of the gang members and calmly says "Bang." The guy immediately falls down, shot. Dwight does the same to the second one. Randall enters from outside. He is holding a smoking gun wrapped in a towel.

Scully and Doggett investigate the crime scene, finding that the shots came from behind a wall, landing perfectly on their targets. Scully theorizes that the killer could see through the wall and Doggett dismisses her claims. She conjectures that maybe this man's eyes are somehow different than normal. Doggett believes that it was merely a drug hit. Yet after finding sulfuryl fluoride, an exterminator's chemical, on the towel scrap, he suggests they go to the exterminators named on Chase's invoices. Meanwhile, Dwight takes Tammi into a back office and she begins to undress. She senses that Randall is always watching her, and Dwight laughs her off. "How's he watching you now?" he asks. Randall stares at the door to the office, but then turns away when he hears someone coming into the building. Doggett and Scully enter, and Dwight greets them. They show him an invoice from Chase's office, but Dwight is unable to read it because he has been legally blind since childhood. He calls for Tammi, and she comes out of the office buttoning her blouse. Doggett asks why Chase called their office 14 minutes before he was killed. Tammi looks away shamefully. Dwight seems surprised, but he tells them that no message was left that night. The agents leave and Dwight confronts Tammi about the message. She admits that there was a message that she accidentally erased.

Scully and Doggett research Dwight's criminal record. He was arrested for grand theft auto, but since he is almost blind, they assume he had used a partner. They search for Randall's record and find that the two brothers are twins. In her apartment that night, Tammi is frightened by her next door neighbor's shadow on the window outside. She can't see that it is really Randall, watching her undress through the walls. Early the next morning, Tammi rushes into the office. Dwight and Randall catch her grabbing the lock box, but Scully and Doggett storm in with a search warrant. Although the lock box is empty, Scully finds a ledger with Chase Realty information in it. They bring the brothers in for questioning. As Scully interrogates Randall, he stares at the wall behind her and reads his brother's lips in the room next door. Randall repeats Dwight's statement that he is just a "regular Joe, providing a public service." Scully opines that he can see through the walls. She says that she knows about him shooting drug dealers through walls to steal their money. As the agents bring in Tammi for questioning, Dwight nods toward the girl and tells Randall that they have a problem that needs to be "taken care of." In the interview room, Tammi offers that she only keeps the books for the brothers and doesn't know anything about the drug dealers. Surmising the case, the agents believe that Chase was Dwight's fence for the drugs and was killed because he had a relationship with Tammi. Her phone records indicate she called him late at night.

Tammi again sees the shadow outside her apartment, and it moves when she calls out to Randall. She tells him that she knows he protected her and that he snatched her secret ledger book so Dwight wouldn't find it. She still, however, needs his help. She asks Randall to meet her at the 3:00 bus, and he gives her the missing ledger that holds a key. Finding Tammi's apartment emptied out, Doggett hits redial on her phone and reaches the bus station. Tammi uses the key to grab a duffel full of cash in a safe deposit box at the bank. When she returns to her car, Dwight is waiting in the backseat. He forces her to drive to the office. Left at the station, Randall believes he's been stood up. At the exterminator's office, Dwight accuses Tammi of skimming from the books with Chase. He questions why Randall would kill Chase, and then figures out that his brother has a crush on Tammi. Randall enters, and Dwight orders him to kill her. Randall points the gun at Tammi as she pleads for her life. He fires, but the bullet sails inches from her head to hit Dwight, who is outside having a cigarette.

Scully and Doggett arrest Randall, but he will not speak. He sits motionless in a cell, eyes focused on a blank wall. Randall stares at a computer monitor located many rooms away. On it is an all-points bulletin for the arrest of Tammi Peyton, with her image emblazoned on the screen.