It is dark when Detective Arbogast returns to the Bates Motel. He goes into the office, but Norman Bates isn't there, so Arbogast goes into the parlor and observes the stuffed birds. He also finds a safe on the ground, which is open and empty. He then decides to make his way up to the house, where the lights are still on.
The door to the Bates home is open, and Arbogast lets himself inside. He makes his way up the stairs, and the camera is in front of him. Then, the background starts to go into soft focus and Arbogast gets smaller and smaller in the frame. The door at the top of the stairs slowly creaks open, letting out a shaft of light. Cut to a bird's eye view of Arbogast reaching the top of the staircase, just as Mrs. Bates comes rushing out of the door with her knife raised. She stabs a shocked Arbogast, and the camera stays on his bloody face as he tumbles down the staircase and lands on the ground, where Mrs. Bates finishes him off. The film fades out.
When we fade in, Lila and Sam are nervously waiting for Arbogast in the hardware store. It has been three hours and they haven't heard from him yet. Lila feels as though something is wrong and insists on going out to the Bates Motel herself. Sam tells Lila to wait at the hardware store in case Arbogast returns; it is better for him to go to the Bates Motel because he knows where it is. Meanwhile, Norman is at the edge of the swamp again, insinuating that he has gotten rid of Arbogast's car and body in the same way he disposed of Marion's. Sam arrives at the Bates Motel and, seeing no trace of the man, he calls out Arbogast's name. The camera tracks into Norman's face as he hears Sam's voice, but his expression is obscured in darkness. He does not move to welcome his new visitor.
Later, Sam returns to the hardware store where Lila is waiting. Arbogast hasn't returned, and Sam tells Lila that he could not find Arbogast or Bates, either. He did, however, glimpse the old lady in the window - but she was either too sick to answer the door or unwilling to do so. Sam and Lila speak in a medium two-shot, but their faces are cloaked in shadows. Sam suggests they go and pay a visit to Al Chambers, Fairvale's Deputy Sheriff.
Al Chambers (John McIntire) comes down the stairs of his house in his bathrobe. He and his wife, Mrs. Chambers (Lurene Tuttle) listen as Sam and Lila explain their situation. Chambers, a grizzly and unemotional man, asks some basic questions about Marion's disappearance. Sam explains that they don't want to formally involve the police because they are hoping to coerce Marion to give back the money without Cassidy and Lowery taking legal action against her. Lila, who is certain that something is amiss at the Bates Motel, insists that Chambers call Norman Bates to see if he can get any answers. Chambers reluctantly calls Norman and asks him about Arbogast. Norman admits that Arbogast was at the motel, but he simply asked some questions and then went on his way.
Irritated with Lila's continued insistence that Norman isn't telling the whole truth, Chambers finally insists that Arbogast couldn't have gone back to see Norman Bates's mother because the old woman has been dead and buried for the past ten years. Chambers explains that in the only murder-suicide on Fairvale's ledgers, Mrs. Bates poisoned her lover when she found out he was married and then took a helping of strychnine herself. Now, Lila is certain that there is something not right here because Sam has seen Norman Bates's mother in the window, and presumably, so had Arbogast.
Jean Douchet writes about the three planes of reality that Hitchcock explores in Psycho. There is the everyday world, like the Phoenix hotel, Marion's office, and Sam's hardware store. Then, the second world is one of desire - Marion's theft and frantic drive to California; the parlor and Cabin 1 at the Bates Motel, and the swamp in which Norman hides the evidence of his mother's crimes. Now, as Arbogast, Sam, and Lila start poking around the Bates Motel, we have entered the third reality - the intellectual world. This, which Douchet calls "the main plank of the Hitchcockian oeuvre" (Kolker 65), is what connects the first and the second realities. It is only through the prodding of these newly introduced characters that the audience will be able to discover the true nature of Norman Bates.
To this end, Hitchcock is not at all concerned with fleshing out the characters of Sam, Lila, or Arbogast. We know nothing about Lila other than the fact that she is Marion's sister and lives with her sister in Phoenix. We don't learn anything new about Sam, and Arbogast is a two-dimensional character, as well. However, this is not a misstep on Hitchcock's part, but rather, a deliberate decision to keep the audience's focus on Norman and the mystery of the Bates Motel. Sam, Lila, and Arbogast simply serve the purpose of moving the plot forward, and not much else; that's all Hitchcock (and the audience) needs them to do. In early drafts of the Psycho screenplay, a love affair blossomed between Sam and Lila; Hitchcock cut out these scenes because he did not feel that they were necessary.
Hitchcock was always insistent about not lying to his audience, and that certainly presents a challenge, especially when trying to pull off a plot twist as major as the one in Psycho. During production, Hitchcock kept a director's chair with Mrs. Bates's name on it on set all the time, which he hoped would satiate public curiosity even if nobody were ever sitting there. Similarly, he came up with a number of devices to conceal Mrs. Bates's true identity in the film without making the audience feel like he was trying to hide something. The impressionistic nature of the shower scene followed by Norman's reaction to Marion's murder make it perfectly plausible that Mrs. Bates is a real, live woman. It becomes trickier with Arbogast, though. The detective's murder was also storyboarded by Saul Bass; Hitchcock told Truffaut that one of the reasons that he filmed it from an extreme high angle was "in order not to give the impression that I was trying to avoid showing her". Then, as Arbogast falls, we watch him from Mrs. Bates's perspective.
Arbogast's murder and Al Chambers' subsequent revelation that Mrs. Bates has been dead and buried for the past ten years invoke the popular horror film tropes of the day, like ghosts and haunted houses. Hitchcock purposely designed the exterior of the Bates House to resemble a haunted house. He added in the moonlight, the clouds, and the stormy sky behind the house in post-production to enhance this effect. Then, he uses point-of-view tracking shots to place the viewer with Arbogast as he climbs the stairs into this creepy abode (Hitchcock does the same thing with Lila later in the film). At this point, the audience already knows that there is a murderous force inside the Bates house, and we are conditioned to anticipate that something terrible is about to happen. In the moment when Mrs. Bates comes rushing out of her room, the extreme high angle shot makes the viewer feel helpless as the crime unfolds, and then in the next shot, Arbogast's bloody face fills the screen - now it's too late. As Hitchcock once said, "[Arbogast's] big head has no impact unless the previous shot had been so far away" (Sherman 107).
It is impossible to write about the timelessness of Psycho without discussing Bernard Hermann's score. Hermann (who also scored Citizen Kane) worked with Hitchcock throughout his career in the United States. The entire score of the film is played entirely by strings, and the shrieking effect that accompanies both Marion's and Arbogast's murders makes them that much more jarring. Throughout the film, the entrance of the shrill violins indicates a movement from the everyday world into the world of desire and madness.