Eyes Wide Shut

Dr. Bill Harford (Tom Cruise) and his wife, Alice (Nicole Kidman), are a young couple living in New York. They go to a Christmas party thrown by a wealthy patient, Victor Ziegler (Sydney Pollack). Bill meets an old friend from medical school, Nick Nightingale (Todd Field), who now plays piano professionally. While a Hungarian man named Sandor Szavost (Sky du Mont) tries to pick up Alice, two young models try to take Bill off for a tryst. He is interrupted by a call from his host upstairs, who had been having sex with Mandy (Julienne Davis), a young woman who has overdosed on a speedball. Mandy recovers with Bill's aid.
The next evening at home, while smoking cannabis, Alice asks him if he had sex with the two girls. After Bill reassures her, she asks if he is ever jealous of men who are attracted to her. As the discussion gets heated, he states that he thinks women are more faithful than men. She rebuts him, telling him of a recent fantasy she had about a naval officer they had encountered on a vacation. Disturbed by Alice's revelation, Bill is then called by the daughter of a patient who has just died; he then heads over to her place. In her pain, Marion Nathanson (Marie Richardson) impulsively kisses him and says she loves him. Putting her off before her fiancÃ© Carl (Thomas Gibson) arrives, Bill takes a walk. He meets a prostitute named Domino (Vinessa Shaw) and goes to her apartment.
Alice phones just as Domino begins to kiss Bill, after which he calls off the awkward encounter. Meeting Nick at the jazz club where he's just finishing his last set, Bill learns that Nick has an engagement where he must play piano blindfolded. Bill presses for details. He learns that to gain admittance, one needs a costume, a mask, and the password (which Nick had written down). Bill goes to a costume shop. He offers the owner, Mr. Milich (Rade Serbedzija), a generous amount of money to rent a costume. In the shop, Milich catches his teenage daughter (Leelee Sobieski) with two Japanese men and expresses outrage at their lack of a sense of decency.
Bill takes a taxi to the country mansion mentioned by Nick. He gives the password and discovers a quasi-religious sexual ritual is taking place. Although he is masked, a woman takes Bill aside and warns him he does not belong there, insisting he is in terrible danger. She is then whisked away by someone else, so Bill spends some time wandering from room to room in the mansion, where groups of masked people are engaged in various types of sexual acts, while others watch. He is then interrupted by a porter who tells Bill that the taxi driver wants to speak urgently with him at the front door. However, the porter takes him to the ritual room, where a disguised red-cloaked Master of Ceremonies confronts Bill with a question about a second password. Bill says he has forgotten. The Master of Ceremonies insists that Bill "kindly remove his mask", then his clothes. The masked woman who had tried to warn Bill now intervenes and insists that she will redeem him. Bill is ushered from the mansion and warned not to tell anyone about what happened there.
Just before dawn, Bill arrives home guilty and confused. He finds Alice laughing loudly in her sleep and awakens her. While crying, she tells him of a troubling dream in which she was having sex with the naval officer and many other men, and laughing at the idea of Bill seeing her with them.
The next morning, Bill goes to Nick's hotel, where the desk clerk (Alan Cumming) tells Bill that a bruised and frightened Nick checked out a few hours earlier after returning with two large, dangerous-looking men. Nick tried to pass an envelope to the clerk when they were leaving, but it was intercepted, and Nick was driven away by the two men.
Bill goes to return the costume â but not the mask, which he has misplaced â and Milich, with his daughter by his side, states he can do other favors for Bill "and it needn't be a costume." The same two Japanese men leave; Milich implies to Bill that he has sold his daughter for prostitution.
Bill returns to the country mansion in his own car and is met at the gate by a man with a note warning him to cease and desist his inquiries. At home, Bill thinks about Alice's dream while watching her tutor their daughter.
Bill reconsiders his sexual offers the night before. He first phones Marion, but hangs up after Carl answers the phone. Bill then goes to Domino's apartment with a gift. Her roommate Sally (Fay Masterson) is home, but not Domino. After Bill attempts to seduce Sally, she reveals to him that Domino has just tested positive for HIV. Bill leaves and notices a man is following him. After reading a newspaper story about a beauty queen who died of a drug overdose, Bill views the body at the morgue and identifies it as Mandy.
Bill is summoned to Ziegler's house, where he is confronted with the events of the past night and day. Ziegler was one of those involved with the ritual orgy, and identified Bill and his connection with Nick. His own position with the secret society has been jeopardized by Bill's intrusion since Ziegler recommended Nick for the job. Ziegler claims that he had Bill followed for his own protection, and that the warnings made against Bill by the society are only intended to scare him from speaking about the orgy. But he implies the society is capable of acting on their threats, telling Bill: "If I told you their names, I don't think you'd sleep so well". Bill asks about the death of Mandy, whom Ziegler has identified as the masked woman at the party who'd "sacrificed" herself to prevent Bill's punishment, and about the disappearance of Nick, the piano player. Ziegler insists that Nick is safely back at his home in Seattle. Ziegler also says the "punishment" was a charade by the secret society to further frighten Bill, and it had nothing to do with Mandy's death; she was a hooker and addict and had indeed died from another accidental drug overdose. Bill clearly does not know if Ziegler is telling him the truth about Nick's disappearance or Mandy's death, but he says nothing further and lets the matter drop.
When he returns home, Bill finds the rented mask on his pillow next to his sleeping wife. He breaks down in tears and decides to tell Alice the whole truth of the past two days. The next morning, they go Christmas shopping with their daughter. Alice muses that they should be grateful they have survived, that she loves him, and there is something they must do as soon as possible. When Bill asks what it is, she simply says: "Fuck".

Question: What does Bill misplace?
Answer: the mask; the mask