Unlikely as it may seem, Ruben Brandt embarks on a train journey along with the artwork of Duveneck's Whistling Boy, only to be attacked by Velázquez's Infanta Margarita Teresa, revealing that he has been plagued by nightmares.
An acrobatic thief named Mimi pulls off a daring heist, stealing Cleopatra's Fan from the Louvre Museum. Hired by the crime lord Vincenzo Delangello, she was initially tasked to acquire another valuable item, the le Régent Diamant. However, her kleptomania takes over, leading her to sacrifice the fan for her escape from private investigator Mike Kowalski. Realizing her psychological struggles, she seeks guidance from psychotherapist Ruben Brandt, who specializes in helping artistic souls. He counsels her to "possess your problems to conquer them."
During their sessions, Mimi learns that Brandt suffers from panic attacks and nightmares induced by Venus of Urbino. In a bold attempt to aid him and demonstrate her therapeutic progress, she enlists his other patients — former bodyguard Bye-Bye Joe as well as fellow thieves Membrano Bruno and Fernando — to steal the Venus of Urbino painting for him. By confronting this challenge, they literally embody the advice he gave her. Impressed by their success, Brandt divulges that he has recurring nightmares involving twelve other renowned paintings. Together, the group sets off on a globe-trotting adventure, executing clifftop heists to steal these prized works of art.
As the press dubs the enigmatic thief "The Collector," the stolen paintings, which cannot be sold even on the black market, become a point of intrigue. The insurance company announces a reward for information about the Collector, putting Kowalski on their trail. Meanwhile, Delangello begins to suspect a connection between Mimi and the thief.
In the frame of betrayal, John Cooper, a former colleague of Brandt's deceased father who worked with subliminal methods in the CIA, connects the dots and identifies Brandt as the criminal mastermind behind the thefts. He contacts Kowalski, but before the investigator can arrive, mercenary Kris Barutanski brutally eliminates Cooper in a quest to find the Collector for Delangello. Unbeknownst to Kowalski, Barutanski follows closely in pursuit of him.
Delving into the house of Brandt's late father, Kowalski discovers subliminal film clips depicting the stolen artworks. Flashbacks reveal that Gerhard forced a young Ruben to consume cartoon films instead of allowing him to enjoy outings. In a fierce confrontation, Kowalski ultimately defeats Barutanski, learning in the process that Gerhard Brandt is also his father, making him the half-brother of Ruben, as Kowalski's mother left Gerhard to escape his experimental tendencies.
While Brandt and his accomplices attempt to pilfer a painting by Renoir, they face a police ambush but manage to slip away. Delangello's henchmen trail them relentlessly, yet they too evade capture.
Mimi experiences a transformative dream where she successfully controls her urge to steal. However, when she tries to share this breakthrough with Brandt, he morphs into Kowalski, complicating her feelings.
The group's final target is Warhol's Elvis I, II, located in Tokyo. As Kowalski deduces the painting’s significance, Delangello secretly monitors his movements. Brandt's team devises an elaborate ruse to secure the painting under the guise of a public performance. The plan takes a chaotic turn when Delangello's men recognize them, misinterpreting the ensuing scuffle as part of the act. Ultimately, they successfully steal the painting, which is added to Brandt's extensive collection.
As the film progresses, Brandt appears on the brink of yet another nightmare, but instead, he wakes up peacefully aboard a tranquil train with a personalized art book from his accomplice. In the reflective glass, the silhouette of Kowalski materializes. The journey concludes with the revelation of a solitary train car moving forward, drawing focus to a slow-moving snail, symbolizing the intertwining personal journeys of these complex characters. As Frigyes Karinthy stated at the film's outset, > "In my dream, I was two cats and I was playing with each other."
