Heist of the Centuries

 is a quest in the Fallout: New Vegas add-on Dead Money.

Detailed walkthrough
To begin the quest, the speaker next to the elevator in Vera Keyes' suite must hear the password in Vera's voice. This can be done by piecing together snippets of recorded music from the receptionist terminal in the lobby, after which Christine will repeat the password into the speaker, unlocking the elevator.

Warning: Once the Courier enters the elevator, he cannot return to the Sierra Madre proper until Elijah is dealt with. Ensure that the Courier is carrying sufficient stimpacks and micro-fusion cells for the Holorifle, as there are numerous security holograms, toxic clouds and speakers which must be shot out. Place any extra items in the dresser next to the autodoc, as the Courier will have to discard everything carried in order to escape the Sierra Madre Casino Vault with any appreciable amount of treasure.

The quest begins in earnest once the Courier enters the vault. The central chamber is visible from the elevator, though access is blocked by a force field. The Courier must navigate a maze of ducts and catwalks filled with the aforementioned security holograms, toxic clouds and speakers. In some situtations, the Courier may have to trigger hologram monitors to clear a path.

Immediately before entering the vault is a toolbox; next to it is a holotape containing a venomous message to Vera Keyes, and a skeleton lies on a pipe beneath it - Sinclair's. A bag is next to it, containing a copy of Nikola Tesla and You.

Inside the vault itself is a assortment of weapons, armor, stealth boys, chems, money, chips... and the fabled Treasure of the Sierra Madre: 37 Gold Bars worth 10539 caps each, for a total of 389943 caps and the single greatest collection of wealth in the Mojave Wasteland - each of which weighs 35 pounds, for a total of 1295 pounds.

However, the vault door seals within seconds of entrance. Lift the lockdown using the left security terminal, then use the monitor in the back to look up the word 'Vera'. This reveals that Sinclair in fact designed the Sierra Madre Vault not to protect valuables, but a small number of people as per a Vault-Tec Vault through the Great War: namely himself and Vera Keyes. Knowing that Vera had begun an affair with Dean Domino did not change these plans, nor did Domino's plans to rob the Sierra Madre. Hardware failures meant that the Vault could not be opened from the inside once it was sealed, meaning those inside had no choice but to wait for rescue once sealed in. Sinclar left a warning for Vera, and a trap for Domino: a file marked "personal accounts", the reading of which activates a system which permanently seals the vault.

After the Courier reads this, Elijah will make contact. Skills of 75+ in Lockpick or Stealth can be used to persuade Elijah to enter the vault to confront the Courier personally. He will bypass the duct maze by deactivating a forcefield and walking directly to the vault door, where, if not confronted and killed by the Courier, he will trigger the trap Sinclair meant for Domino and seal himself inside.

Hacking the security terminal in the vault will cause the Turrets outside to turn on Elijah and if they kill him, the player will not receive the Cash out achievement/trophy.

If not killed quickly, Elijah will reactivate the forcefield and activate the Courier's collar, leaving him with only minutes to traverse the duct maze and escape up the elevator shaft before he is killed. If the Courier chooses to engage Elijah in direct combat, Elijah will activate the forcefield as soon as he notices the Courier, and Elijah's death will activate the Courier's collar.

However, the obvious solutions (killing or sneaking past Elijah before he can reactivate the forcefield or the Courier's collar), are not viable options due to programmer fiat: Elijah is immune to damage until he reactivates the forcefield blocking access to the elevator, and becomes instantly aware if the Courier steps onto the stairs below the forcefield, even if the Courier is using a Stealth Boy. Even killing Elijah once the forcefield is reactivated is problematic, as Elijah can pass through it even if it is active, after which he will activate the Courier's collar.

-If the player chooses to sneak past Elijah to the exit, sealing him inside (for the Safety Deposit Box achievement/trophy,) the simplest solution is to simply run back through the basement the way he/she came. If the player runs back through the area as quickly as possible, he/she will arrive at the back side of the maintenance door, which will be temporarily locked. When Elijah arrives at the vault door, after some grumbling, he will activate security, opening the door, and the player can simply walk out and leave Elijah to his fate.

However the Courier handles Elijah causes the explosive collar to activate, which will detonate within a minute if the Courier does not board the elevator to the surface within that time. This is not difficult if the Courier is not overloaded; in fact, the Courier can easily reach the maintenance access door before Elijah reaches the door to the casino vault(in which case it will still be locked by programmer fiat - it will open once Elijah realizes he has been deceived) The implication is that the Courier is expected to discard most possessions in order to carry a small number of gold bars through the duct maze and thus to the elevator.

Reaching the elevator causes the Courier to appear at the fountain in the Villa. The Courier can then revisit any location in the Sierra Madre - and this is recommended; the holographic vendors in the villa gift shop and the casino bar are the only vendors who can easily afford any gold bars the Courier has managed to escape with, exchanging the expensive and heavy treasures for weightless Pre-War money. Once the Courier exits the front gates of the villa, a slide show plays detailing the fates of his three fellow captives, the end of which shows the Courier deposited at the Abandoned BoS Bunker, and unable to return to the Sierra Madre.

Bugs
A bug has been reported preventing the player from leaving after finishing the quest

(360) Bug will act as if maintenance door is still locked and closed, even if opened (Invisible Wall), effectively trapping the player until their collar blows up.

It is possible to make use of the third-person glitch, that lets you activate or interact with things on the other side of walls, to drop all 37 gold bars near the force field Father Elijah uses, run around the long way, and pick them all up as one, from the other side. It all has to do with looking at it at the precise angle while crouched. Think of it as some sort of defect in the force field design.