Detective Doyle looks out Jeff's window and wonders how Jeff can be sure that there was a murder even though he didn't see it happen and there is no body. Doyle thinks it's unlikely that Jeff's suspicions are correct while Jeff tries to convince him otherwise. Doyle eventually agrees to poke around and try to find out where Mrs. Thorwald is, mostly as a favor to his friend. After Doyle leaves, Jeff notices the same little dog digging up the flowers that Mr. Thorwald planted. Then, Mr. Thorwald comes outside with a watering can and shoos the dog away.
Later, Doyle returns to Jeff's apartment to tell him what he has found out: the Thorwalds are in the 5th month of a 6-month lease, they are quiet, and Mr. Thorwald is indeed employed as a salesman of wholesale costume jewelry. Both Thorwald and his wife keep to themselves. Mrs. Thorwald last left the apartment at 6 a.m. the previous morning - she and her husband happened to depart while Jeff was asleep.
Jeff asks Doyle how he knows that the Thorwalds left their apartment at that time. Doyle tells Jeff that the superintendent and two tenants saw them go; the superintendent also saw Mr. Thorwald on his way back and he said that he'd dropped Mrs. Thorwald off at the train station for a trip to the country. Jeff keeps questioning Doyle's information, however. He insists that Doyle search Thorwald's apartment, even though he cannot do that without a search warrant. Doyle produces a postcard from Mrs. Thorwald telling her husband that she arrived at her destination safely. Done arguing, Doyle leaves Jeff's apartment.
That night, Jeff is sitting by the window with a sandwich and his telephoto lens. He watches Miss Lonelyhearts get dressed up and pour herself a drink. Upstairs, the songwriter is entertaining a pair of pretty women, while Miss Torso is practicing her dance moves. Miss Lonelyhearts leaves her apartment, crosses the street and enters a restaurant, where she is clearly waiting for a date. Then, Mr. Thorwald passes in front of Jeff's lens; he has come home from work and is carrying a box of laundry. Thorwald removes clean shirts and handkerchiefs from the box and stacks them on his bed. Jeff calls Doyle's house and tells his wife that Doyle needs to come to his house as soon as possible.
After Jeff hangs up, he watches Thorwald take his wife's handbag into the living room and make another long-distance phone call. While he is on the phone, Thorwald unpacks the contents of the purse, which include a wedding band. Meanwhile, more people arrive at the songwriter's party. Lisa enters and Jeff updates her on everything that has been happening that evening. They watch Thorwald as he leaves his apartment.
Lisa says she's been distracted all day thinking about Thorwald and whether or not Doyle found anything. Lisa doesn't believe that Mrs. Thorwald would leave behind her favorite handbag or her jewelry if she were going on a trip. Lisa speculates that the woman who left the Thorwalds' apartment with Mr. Thorwald was not actually his wife. Jeff sweeps Lisa into his arms and kisses her. She informs him that she's going to spend the night at his apartment. She opens her tiny suitcase/handbag filled with nightclothes in order to show him that she can, indeed, live with very little.
Lisa walks to the window and listens to the songwriter play the piano; she loves the beautiful melody. Doyle arrives while Lisa is in the kitchen. He looks out the window at the songwriter's party, which has gotten very crowded. Doyle notices Lisa's nightclothes on the table and raises an eyebrow, but Jeff warns him not to ask any questions. When Lisa returns to the room, they all sip brandy while Lisa and Jeff share the details of their suspicions with Doyle. Doyle systematically dismisses all of their questions. He managed to track down the infamous trunk, and it was filled with Mrs. Thorwald's clothing. The only reason it was wrapped in rope was because the lock is broken. Nevertheless, Jeff and Lisa remain convinced that something strange is going on. Tension grows between the detective and the couple until Doyle leaves; he's not going to delve into this matter any further.
Jeff, like Hitchcock, is operating behind the scenes of the "investigation." Similar to a film director, Jeff has a crew: Stella, Lisa, and Doyle. He isn't the one taking the physical risks; instead, he directs others to do so. Jeff commands Stella to find out where Thorwald's trunk is going, he sends Lisa to find out the salesman's name and tells her when to raise and lower the lights, and he demands that Doyle investigate a murder for which he has no proof. He even gives his neighbors false names, as if they were actors in a grand performance of his design.
Therefore, Hitchcock uses the character of L.B. Jefferies to explore the morality of being the "man behind the camera." Earlier in the film, Stella is the one who warns Jeff against poking into others' business. In this section, Doyle takes on the role of the moral police, pointing out that Jeff is putting others at risk in order to satiate his own curiosity. Doyle draws a parallel to their time at war, saying, "If I'd have been careful piloting that reconnaissance plane during the war, you wouldn't have had the chance to take the pictures that won you a medal and a good job and fame and money." Just like a movie director, Jeff's success in this venture relies on the hard (and often under-appreciated) work of others.
Hitchcock explores Jeff's major character flaw in this section as well, which is his stubborn and hypocritical behavior. For example, he acts like an authority on morality while he is spying on his neighbors' private lives - refusing to give Thorwald the benefit of the doubt, and deriding Miss Torso's supposed hunt for the richest and most successful suitor. Then, when Jeff catches Doyle ogling Miss Torso, he sneers, "How's your wife?" Meanwhile, Jeff has been watching Miss Torso for weeks, even though he has a girlfriend. Furthermore, Jeff, as a journalist, considers it his moral obligation to report on the suspicious goings-on around the courtyard, but he does not respect Doyle's professional responsibilities to adhere to certain rules and regulations; Jeff keeps insisting that Doyle investigate Thorwald's apartment, while Doyle has to remind him that the penal code and the constitution prohibit him from doing so. Once again, Jeff is asking someone else to take a risk for him, but neglecting to see the danger because he is so far removed from it.
Meanwhile, Doyle acts as a purveyor of truth and tries to counter Jeff's hypocrisy, but Jeff won't listen. When Jeff wonders why Thorwald never told their landlord about Mrs. Thorwald moving out, Doyle points to Lisa's nightclothes, asking, "do you tell your landlord everything?" Jeff warns Doyle to be careful; but Doyle is simply pointing out that Jeff hasn't been at all careful in making assumptions about his neighbors, so why should Jeff be exempt from such scrutiny? Despite Doyle's challenges, though, Jeff refuses to accept any of the hard facts that Doyle lays out for him about the Thorwalds. Instead, he insults the detective time and time again, even though Doyle has gone far above and beyond the call of duty. Jeff chooses to remain in his protected bubble and to project his problems onto everyone else: It's his editor's fault that he can't go back out on assignment; it's Lisa's fault that he can't marry her; and it's Doyle's fault that Mr. Thorwald might get away with a crime.
Unlike Doyle, Lisa has become savvy to Jeff's ways. In this section, she shows that she has learned that the only way for Jeff to see her as a true life partner is to first become his partner in the "investigation" - she basically uses the Thorwald case to seduce Jeff. "I'll trade you," she says, "my feminine intuition for a bed for the night." This time, when Lisa kisses Jeff, he is no longer distracted by his neighbors - because Lisa is talking about the Thorwalds while they are making out. When she offers her own insights into the case, Jeff gives her his full attention and affectionately replies, "I'm with you, sweetie, I'm with you," as opposed to his mocking comments when she told him about her day a few nights before. Jeff does burst Lisa's bubble eventually, pointing out that detectives rarely marry the "Girl Friday", but instead of giving up, Lisa only works harder. She goes on to express her solidarity with Jeff when Doyle arrives. "We think Thorwald is guilty," she tells him. Even though Lisa herself questioned the morality of Jeff's spying earlier in the film, she now leaves that to Doyle. Hitchcock further emphasizes Jeff and Lisa's united front by framing them in a two-shot together vs. Doyle in a medium shot alone.
Despite Lisa's best attempts to sway him, Jeff refuses to change his opinion on marriage, even though all of couples in the apartment complex offer "a different possibility of [Jeff's] life with Lisa" (Spoto). Jeff sees the newlyweds, who are blissful in each other's company; he sees the couple that sleeps on the fire escape. He sees the loneliness that defines the lives of the singles like Miss Lonelyhearts, Miss Torso, and the songwriter. However, instead of trying to recognize the good things that could come from marriage and accept the negative aspects of being alone, Jeff zeroes in on the Thorwalds. From the beginning of the film, he looks at them as the only version of marriage that he can accept because it fits with his preconceived notions. Early on, Mrs. Thorwald nags and fights with her husband; Mr. Thorwald becomes so tired of her that his only recourse is murder. It does not even matter at this point whether or not Jeff is right about Mr. Thorwald; his insistence on Thorwald's guilt is a manifestation of Jeff's internal barriers against a committed relationship.