Back in Paris, Eames explains that the idea incepted in Robert’s mind must seem self-generated. Late one night, while fashioning her totem, Ariadne finds Cobb, who tells her that his totem used to belong to Mal, who came up with the idea to keep track of reality. Cobb divulges to Ariadne that he can’t go home because he’s under suspicion of killing Mal.
Later, Cobb, Eames, and Arthur discuss the contours of the idea they will need to incept. Eames suggests a positive, rather than a negative, motivation for Robert’s decision, to be seeded in parts over three layers of the dream. Each layer will distort time further and further, from a week, to six months, to ten years. Yusuf explains that he has customized the sedative to be responsive to a “kick”—a falling motion that jolts the dreamer out of the dream. Arthur suggests using a song to synchronize the kick across the dream’s three layers. The team decides to stage the ten-hour inception by sedating Robert Fischer while he is traveling from Sydney to Los Angeles on a 747 airliner.
Late one night, Ariadne enters Cobb’s dream and descends in an elevator to find Mal soothing him in a large living room. Cobb scolds her for entering his dream unprompted, and the elevator ascends up to a beach, where they see Mal playing with Cobb’s children. Ariadne realizes that Cobb is using his memories to dream, despite the fact that he warned her not to do the same. Cobb’s desperation frightens Ariadne.
Ariadne runs from Cobb and rides the elevator down past a roaring train to the basement level, where she finds a ransacked hotel suite. There Ariadne finds Mal, who threatens her with a broken wine glass, before Cobb arrives and explains this suite was where he and Mal spent anniversaries. Cobb ushers her back into the elevator, and when they wake up, Ariadne chastises Cobb for thinking he can contain Mal in the “prison” of his memories.
Maurice Fischer dies in Sydney, prompting the team to take sudden action. Ariadne insists on coming along, although Cobb is reluctant to take her, in order to honor Miles’s wishes. Eames and Cobb take their seats next to Robert Fischer in the first-class cabin of the plane. Cobb casually strikes up a conversation with Robert and slips a sedative into his drink, toasting to his late father. Once Robert is unconscious, the rest of the team connect themselves to the “dream sharing” technology and a flight attendant hits a button, causing them all to simultaneously enter Robert’s dream.
In Robert’s dream, Yusuf stands on a street corner in the rain before a car containing Cobb, Arthur, Saito, and Eames picks him up. While driving, Cobb intentionally bumps a taxi ahead with his fender. The taxi driver steps out and Cobb holds him at gunpoint while Arthur hijacks the vehicle. Arthur picks up Robert as a passenger in the taxi, and Eames enters right behind him, posing as a pushy stranger. When Robert protests, Saito points a gun at him from the passenger seat.
Behind them, Cobb ushers Ariadne into his vehicle, which is then violently struck by a freight train plowing through the middle of the street. Robert is about to offer cash to Saito when the dream’s human projections start a chaotic shootout in the street. Ariadne, who did not design the intrusion of the train, immediately becomes concerned.
The totem is one of the key symbols in Inception. Cobb is first seen using his—a small, spinning top—in his Kyoto penthouse in the first act of the film, and the viewer learns that it originally belonged to Mal. As a handmade token, the totem is an object that tells its owner definitively whether or not they are dreaming. Cobb telling Ariadne that the totem was Mal's idea is a piece of foreshadowing that suggests that Mal had begun to have trouble distinguishing dreams from reality. Cobb's confession that he is under suspicion for killing Mal also gives the viewer crucial information as to why he is desperate to carry out the inception plot.
Although Mal is present in the film from the opening scenes, the nature of Cobb's relationship with Mal is only gradually revealed to Ariadne and to the viewer over the course of the plot. Nolan constructs a "theater of memory" around Cobb's sentimental recollections of Ariadne that have crumbled over time, such as the ransacked hotel suite where they used to spend anniversaries. The violent, self-destructive urges that Cobb's guilt over Mal instills in him always erupts in violence, such as when Mal moves to stab Ariadne with a broken wine glass, or when she shoots Arthur in the first sequence. Mal represents Cobb's uncontrollable self-sabotage, which Ariadne worries will compromise the inception mission.
Nolan models the repressed layers of Cobb's consciousness by using the visual and spatial metaphor of an elevator descending and ascending to the various levels of Cobb's mind. For instance, Ariadne rides the elevator down to the "ground" level, where she finds Cobb and Mal speaking in hushed, intimate tones. Ariadne later rides the elevator down to a subterranean level where a more distraught Mal threatens Ariadne. The implication of Nolan's architectural imagery is that Cobb's attempt to repress Mal in the deepest recesses of his mind has only made his turbulent feelings of unresolved guilt fester and grow more harmful to his psyche.
Ariadne accuses Cobb of keeping Mal trapped in the "prison" of his mind, and in fact every character's dreaming mind in Inception resembles a kind of militarized prison or fortress. In Nolan's vision, dreams are often spaces of paranoia where "projections" in the dream can turn against the dream-sharer at any moment. Nolan often contrasts the hyper-realistic veneer of the shared dreams with explosive eruptions of hostile elements, such as the freight train plowing down the city avenue, or the ambush of assault rifle-wielding assailants. These intrusions clue Ariadne and the rest of the team into the fact that Robert has been trained to militarize his subconscious.
In this way, Nolan shows that dreams can be not only a serene realm where old memories are activated, but also a volatile arena where conflicts between opposing political factions are decided. Saito's desire to see the Fischer estate collapse is the film's "MacGuffin"—a name for any central or driving plot device that is pursued with little to no narrative explanation. What the viewer does know is that Saito has the ability to clear Cobb's name and grant him entry back into the United States to see his children, and this emotional hook is what motivates Cobb's tireless labor to make the inception plan a success.