Museum Piece

Museum Piece is a mission given to Niko Bellic by Ray Boccino in Grand Theft Auto IV. In this mission, Ray wants Niko to sell the load of diamonds they obtained in the earlier mission to a buyer at a deal in a museum. Johnny Klebitz will be there as well with Niko to provide support and take his cut of 1 million back to The Lost Brotherhood.

Overview
Ray sends Niko to the the Libertonian museum in midtown Algonquin. Niko meets up with Johnny at the side door of the museum. Their diamond deal is ambushed by a gunman. Niko shoots his way out of the museum and loses the attention of the police and Isaac's crew. Johnny does the same seperately.

Walkthrough
After the initial cutscene, head over to the Libertonian museum in Middle Park, Algonquin. Meet Johnny at the side entrance. They meet the buyer, Isaac Roth with his men inside. A cutscene shows the diamond deal ambushed by Luis Fernando Lopez. Johnny takes the money and flees, and Luis steals the diamonds from Isaac, while Niko has to shoot his way out of the museum.

Remain in cover and take out any Mafia or Jewish Mob members. Move forward down the lane and regain cover when Niko begins to lose health (or armor). Return fire to everyone that is in sight. Once the player is at the end of the lane, turn left and left again to go down the stairs. Shoot the enemies coming up the stairs and get in cover near the bottom of the stairs.

Kill the rest of the Mafia and Jewish mobsters (take your time) and go out of the door. Follow the path until you get out of the museum. Eliminate anyone in the way. Once Niko gets outside, shoot down the drivers of the cars parked outside and lose your wanted level. Isaac's Crew will give chase in their cars, attempting to kill you, once you have lost them you will call Ray and explain what happened. (The achievement/trophy Impossible Trinity is gained on completion)

Tips

 * Make sure to get the armor pickup once Niko gets to the bottom of the stairs. It's hard to miss, but go left at the bottom of the stairs and find the armor in a small, low booth.
 * If the player is quick enough he can kill Johnny without failing the mission.
 * An SMG would be useful in this situation as it can neutralize some of the goons.
 * A good strategy is to use Dwayne's special ability and get 2 of his goons to back you up.

Deaths

 * Mori Green and two unnamed bodyguards are shot and killed by Luis Lopez while observing the diamonds.
 * Two of Issac Roth's goons are gunned down by Luis after the deal is disrupted.
 * Many members of the Mafia are killed by Niko on his way out of the Museum.

Trivia

 * This mission is seen again as Collector's Item in The Lost and Damned, this time from Johnny's point of view and again as Not So Fast in The Ballad of Gay Tony, this time from Luis' point of view.
 * The Desert Eagle is first introduced without cheating, many Jewish Mobsters apparently hold them.


 * If the player wanders back to where the deal took place (during the mission) they can find Issac Roth hiding behind some crates bad-mouthing Ray Boccino, and mourning the loss of Mori Green, though in Not So Fast, Luis Lopez knocks out Issac and takes the diamonds right from his hand. If Issac is killed, the mission will fail (text displayed will say "Issac is dead.").
 * Before descending to the bottom floor, the player can shoot at the hanging dinosaur bones, if done properly, the bones will fall onto unsuspecting mobsters below.
 * After successful completion of this mission, the Xbox 360 Achievement/PS3 Trophy Impossible Trinity is unlocked. In The Ballad of Gay Tony, completing the mission will unlock the Diamonds Forever achievement.
 * The achievement, Impossible Trinity, refers to the three protagonists in GTA IV and its episodes coming in one place which happens only once in each game.
 * During this mission and Collector's Item, Luis is not seen during gameplay. He would not be seen anyway as he snatches the diamonds and escapes upwards, before Niko and Johnny are out.
 * If you go around back where Johnny enters you can see a Hellfury, because the Hexer was not integrated into the series at that point.
 * If you are quick enough and follow Johnny out his exit, he becomes a random pedestrian and walks around instead of escaping. He also has unlimited health even if attacked by the Jewish Mob. Only the player can kill him.
 * If you go back to where the deal took place, you will see three corpses, however, instead of Mori Green, there will just be an old fat Jewish man in his place.
 * After escaping the museum, the instructions state to "Lose Issac's Crew", although if you kill the pursuers and look at their bodies, they are actually Ancelotti goons.
 * It is revealed in The Lost and Damned and The Ballad of Gay Tony in both Johnny and Luis' point of view that Niko used a SMG in this mission.
 * Most of the mobsters are replaced with policemen in The Ballad of Gay Tony, which leads to a continuity error.