Three Leaf Clover

Three Leaf Clover is a mission in Grand Theft Auto IV given to Niko by Patrick McReary.

Description
Niko meets Packie, Michael and Derrick at the McReary Residence in Dukes. After a brief introduction, the group drives to the Bank of Liberty on Columbus Ave in The Exchange, Algonquin. Armed and wearing balaclavas, Michael holds the customers hostage in the foyer, whilst the other three head to the vaults. After making their way into the vaults, the group steal $1,000,000. However, Michael is killed by Eugene Reaper, who is killed in retaliation by Packie and Derrick. The surviving trio return to the street and find themselves surrounded by NOOSE and LCPD officers. After fighting their way to a subway station, the group escapes via the underground subway tracks, eventually returning to the overground and stealing a Huntley Sport to make their getaway. After evading the police, Niko drives Packie and Derrick back to the McReary Residence. Packie mourns Michael's death but congratulates the rest of the group for pulling off the heist, and he gives Niko his share of $250,000.

Mission Objectives
In order to complete the mission the player must:
 * Go to the bank.
 * Go down to the vault and get the money.
 * Cover Packie and Derrick.
 * Follow Packie and Derrick.
 * Get to street level.
 * Find a four door car and go to  Packie's Ma's house. 

Weazel News (Radio)
"The daring heist took place at a Bank of Liberty branch in Downtown Algonquin earlier. One of the robbers was killed in the raid. He was identified as Michael Keane, a felon from Dukes. A bank customer, computer engineer Eugene Reaper attempted to stop the robbery and was murdered. Authorities are on the lookout for three suspects.

Liberty Tree Newspaper
"A daring raid on a downtown branch of the Bank of Liberty has left one robber dead along with multiple police and civilian casualties. The suspect has been identified as Michael Keane, a convicted felon from Dukes. Four men wearing suits and balaclavas entered the branch and held the customers hostage while blowing the door to the vault with explosives. In the confusion, brave customer Eugene Reaper attempted to stop the robbery and was murdered in cold blood. Three robbers left the bank on foot and fought their way through police before escaping on the subway. Authorities are questioning all known associates of Mr. Keane in an attempt to discover the identities of his accomplices. The Bank of Liberty estimates that in excess of half a million dollars was stolen."

After the Mission

 * Gerald McReary will call Niko and ask to meet him in Dukes.
 * Packie will call Niko and ask him to meet Derrick at the Acter Park.
 * Packie will also be available as a friend after he phones Niko later on.
 * It's possible to call Roman after completing the mission. He will ask Niko if he has heard about the bank robbery on the news and tells him he bets his cousin wished he pulled off a job like that, to which Niko will reply he actually was involved in the heist, much to Roman's surprise. Niko will also talk about the McReary family and when he mentions Kate, Roman asks if "they two are doing it" before Niko hangs up.
 * The terrorist threat separating both sides of the West River is lifted, opening up the Booth Tunnel and Hickey Bridge. Niko is able to travel to Alderney legally, with the entire map now open to the player.
 * This will also unlock the Full Exploration achievement on the Xbox 360 and PC versions or, if the PlayStation 3 version is being played, the player receives the Full Exploration trophy.
 * The balaclava is now added to Niko's wardrobe.

Deaths

 * Michael Keane - Killed by Eugene Reaper in an attempt to intercept the robbery.
 * Eugene Reaper - Killed by Packie and Derrick as retribution for killing Michael.
 * Several LCPD and NOOSE officers - Killed by Niko (optional), Packie, and Derrick for trying to stop them from escaping with the stolen money.
 * Luis Fernando Lopez (optional) - Can be shot once the cutscene of the police arriving to the bank concludes. Killing Luis is not canon, since he re-appears in later missions, and in The Ballad of Gay Tony, where he is the protagonist.
 * Hostages (optional) - A couple of the hostages can be killed in this mission, though it is unlikely that this is canon, as killing more than three hostages will likely fail the mission.

Trivia

 * The mission's name is a reference to the three-leafed Shamrock clover commonly related to St. Patrick, the patron saint of Ireland. It may also be a reference to rarely found four-leafed Shamrock clovers, which are thought to bring good luck. There are four members of the heist, with the fourth, Michael, being killed. Niko will remark on his death being unlucky while they escape through the subway tunnel.
 * If Niko touches the hostages, they will die inexplicably. This is most likely an oversight.
 * During the cutscene, Derrick is holding a Pistol, but during gameplay, he uses an Assault Rifle.
 * The general setup and execution of the heist is based on the heist featured in the 1995 film '. Eugene Reaper killing Michael is based on a scene from the 1991 film ' where one of the hostages kills a bank robber before being murdered himself.
 * This mission reappears in both of GTA IV's episodes. The scene of the shootout on the street appears in the end credits of The Lost and Damned, and the scene inside of the bank (ending with the vault exploding) was used as the opening cutscene of The Ballad of Gay Tony.
 * Although the mission can be done any day of the week in-game, I luv LC establishes that the heist canonically took place on a Saturday afternoon.
 * Even if there were no hostages killed (except for Eugene Reaper), Weazel News' radio bulletin will still report “multiple civilian casualties”..
 * This mission is referenced in Grand Theft Auto V. If Packie is hired as a gunman for The Paleto Score, he shares a detailed overview of the mission, from how Michael Keane was fatally shot, the overwhelming police presence, and how they had to enter the subway tunnels to escape. After Packie finishes describing the heist, Michael expresses his surprise at Packie being one of the gunmen.
 * Part of the LCPD commercial used to advertise Grand Theft Auto IV was filmed in reference to (or in the pre-release of) this mission. In the commercial, Officers 1214 and Joey walk past two men, one of whom is carrying an Assault Rifle, wearing balaclavas. These men appear to be Michael and Packie.