I did some watching and skipping around. Rewatching some bits and comparing them to other parts of the movie. I've rewatched the masked ball several times, and here is the sequence of events AS THEY HAPPEN IN THE MOVIE, followed by my current opinion on the situation. I will let you know when I switch from Objective (it happened definitely in the movie) to Subjective (my interpretation of events; what they mean in the big picture).
The Masked Ball (just the facts)1. Tom Cruise arrives at compound. He leaves his "stuff" in the taxi (I am assuming stuff like his man purse, although it is never shown on camera. He mentions it to the driver). He gives the password at the gate and enters the house.
2. In the house, he gives the password again when prompted, hands over his coat to the doormen, and puts on his mask. Note that he does not put the mask on until he is in the house, and his face has been seen by the masked doormen.
3. During the "benediction" scene, two figures on the balcony look at, and acknowledge Tom Cruise. The one with the slanted jaw, mouthless mask is Sydney Pollack. Note that nods are exchanged between Pollack and Cruise, with Pollack initiating.
4. Following the "benediction," the girl with the headdress takes Tom Cruise. This is Mandy, the hooker from Sydney Pollack's office that ODed on speedballs at the beginning of the movie, who was saved by Tom Cruise.
5. Mandy issues a warning to Tom Cruise, telling him to leave. After giving him the warning, they are interrupted by a man in a flesh-colored mask. He takes Mandy upstairs.
6. Tom Cruise walks around the mansion and sees a lot of freaky deaky sex.
7. After wandering through a few rooms, Sydney Pollack and a masked woman are seen watching Tom Cruise from a slight distance. Note that it is not the woman that was with Pollack earlier on the balcony. Pollack says something to the woman, and then he leaves the room.
8. I forget what 8 was for.
9. The masked woman approaches Tom Cruise, and asks if he would like to go somewhere more private (an odd request, what with all the public freaky sex). Before he can leave, Headdress Woman/Mandy returns, quickly into the room, and takes Tom Cruise away. She says she will bring him right back.
10. Mandy again warns Tom Cruise. During the warning, a man with a gold mask (as worn by the doormen, indicating he was an usher of sorts) approaches Tom Cruise and tells him his taxi driver, waiting outside, needs to speak to him. The doormen then takes Cruise to the red-robed master, or whatever.
11. Yada Yada, we see Sydney in the crowd, not in a prominent place, along with the woman that asked Tom to go somewhere private. The master does his thing, and then Mandy shows up on the balcony, and does her thing, apparently exchanging herself so that Cruise can be saved.
12. After her offer is taken, and Cruise is given his warning not to meddle by the master, the next scene is in Cruise's apartment. We do not see his exit, not the taxi ride home.
Details (these are pretty much objective)-Cruise's walk through the mansion is reminiscent of his walk through the party. The way that it is filmed and even in the way the mansion is decorated.
-When Mandy takes Cruise away from Sydney's woman, she says that she will bring him right back when she is done. In the beginning of the movie, when the usher takes Cruise away from his model babes at Sydney's party, Cruise remarks that he will be right back. In both cases, he does not return. In both cases, Cruise was being taken from temptations he was considering.
-When Cruise is being confronted by the master, in the same room as the benediction, the camera goes the opposite direction as it did during the benediction when it is circling the action. I just thought that was a nice detail.
-At Pollack's party, Cruise warns Mandy. At the masked ball, Mandy warns Cruise.
-The only identifiable people in the masked ball are
1. Tom Cruise (duh)
2. Sydney Pollack - Mask with slanted jaw. Identifiable by his eyes.
3. Mandy - Girl in headdress. Identifiable by her, well, large and distinctive titties that you see earlier in the movie when she is ODed and naked.
-There are several interesting side details about the party. Between all the scenes that Cruise views when walking through the mansion, there appears to be some sort of hierarchy amongst the party-goers. There are women that are clothed, women in thongs (otherwise naked), and completely naked women. Men are either clothed or naked. Seeing the groupings, there appear to be some "rules" that can be assembled, but I am not watching the masked ball scene another 4 times to figure things out!
My opinions (here be the subjective shit)I stand by my original interpretation, and maybe I even think that more of the party was a ruse than just Mandy's "sacrifice."
Look at it this way: Cruise's identity was compromised before he even entered the party. His shit was in the taxi (the only taxi there, waiting conspicuously outside the gate--it is later confirmed he had the only taxi there), the people at the gate saw his face, and the doormen in the house saw his face. If these parties are regular things, it stands to reason that the same doormen and guards are used (heck, they use the same blind-folded PIANO PLAYER), and that either they 1) know the regular attendees, or 2) maybe expect different mask-wearing behavour (for example, for something as anonymous as this, I'd expect the face to be covered before even entering the mansion grounds). No matter which of those two was the expected behaviour, Cruise had already given himself away, and there could have been evidence to his identity amongst his "stuff" in the cab.
And even if there was no evidence with his stuff, Pollack later on confirms (during the big reveal scene later in the movie) that the doormen found a receipt from the costume store with Cruise's name on it.
Cruise spends quite a bit of time staring at the "benediction," giving plenty of time for his identity to propagate among whispers and the like. It is not until late in the benediction that Pollack looks and nods at Cruise. The woman with Pollack then also turns to look at Cruise, but she is unidentified. I believe she was there so they could have the creepy visual effect of Pollack and her turning simultaneously to look at Cruise with their freaky masks.
After Mandy warns Cruise for the first time, the man with the flesh-y mask takes her upstairs. Nobody else is going upstairs at this time, and the top of the staircase appears dark, making it, you know, not seem like a party area. I think at this point, the flesh-y man took her upstairs, away, to some clandestine location where the "play" was set up, for when Cruise is confronted at the end of the ball. To back this up, when Mandy returns to get Cruise from Pollack's woman, she seems to do so with a purpose. She shows up again, pulls Cruise into the hallway, and that is where the usher shows up to lead Cruise away. Mandy took him to that hallway, and the usher was there to pick him up. In short, it was a setup. After that, the whole little confrontation with Mandy's sacrifice, that was just a play, set up in advance to, as Pollack later says, scare the shit out of Cruise.
This leaves us with a few questions. What about the woman that Pollack says something to, that then approaches Cruise and asks for privacy? That was Sydney Pollack's way of trying to help Cruise. His plan just never had time to work its magic, since Mandy interrupted it. I expect that "privacy" to Sydney's girl meant "taking him the fuck away from the party."
Another question is how Mandy knew it was Cruise under the mask. She was taking part in the benediction, wrapped up in the ceremony, so it is unlikely that she heard whispers about the infiltration. The only explanation for this is that Cruise's identity was compromised at the front gate, not the door, since that would have given the group time to plan before the benediction even started, before Cruise entered the house. Maybe they didn't know who he was until later, maybe when they had the coat, but when Mandy first approached him, it was a known, definite fact that he did not belong there.
But why then, did Mandy warn him that first time? Up until now, we assumed that her warning was a "thank you" for saving her life from an OD. Well, it turns out that's WRONG. She was warning him because it was a setup from the beginning, and that was what she was told to do. To show that she was not warning Cruise as a "thank you," look at it this way: she died of a drug overdose after the masked ball. A likely coincidence, but this is a fact that comes from Pollack, Cruise's friend. He says it was just a coincidence, and I mean, we do
know she was a junkie hooker.
So that's that, Ichirou, the little play, all of Mandy's behaviour at the masked ball, that was all a ruse. Mandy was never trying to help Cruise there, not for a minute. She probably didn't even know that Cruise was the person that had earlier saved her life. We know she was not good with drugs (she ODed once before during/after a party, why not a second time), and as a hooker, we know her loyalty can be bought. We also know that Pollack was loyal to Cruise. He invited him to Christmas parties that were apparently several levels above Cruise's caste, and he offered to buy him a case of 25 year old scotch, which would be super expensive (also note that he offers to buy the scotch during the big exposition scene. I doubt he would buy a fuckton of very very expensive scotch for someone whose days were numbered).
So that's that. I've dotted my 'i's and crossed my 't's; that's what happened, and Cruise was in no danger, he was just being freaked out.
I win at Kubrick movies!
And FUCK, I forgot Ichirou was banned

FUCK MODS, thanks for wasting my text! He'd better be back.