- Steve Haines: "My sources are convinced there's a plot in International Affairs, y'know 'The Agency', and they're using this facility to make a serious nerve toxin--"
- Trevor: "Haha, bullshit!"
- Steve Haines: "Yeah. Which they plan, in their mind blowing insanity, to let a major terrorist release on a metropolitan area, so they can continue to get funding."
- —Steve Haines in the intro cutscene.
Michael, Franklin, and Trevor meet at Cape Catfish. Soon, Agents Haines and Dave Norton arrive. Haines wants the protagonists to steal a chemical weapon from the Humane Labs and Research, an IAA research facility. Haines is angry due to a lack of manpower (he claims that he told them that it's a six-man job, when he actually didn't). However, he and Norton agree to join the heist. Haines instructs Trevor and Franklin to handle transport, while Michael joins the agents in infiltrating the lab.
Michael and the agents, dressed in scuba suits, take a Dinghy down the San Andreas coast to a spot near Humane Labs and Research. The three dive and approach an underwater exhaust shaft; to gain entry, the player as Michael must use a torch to cut loose a grate over the shaft's access point. Once inside, the three swim through the shaft until they reach the interior of the lab. From there, the three advance through the halls. Michael is armed with a stun gun and is responsible for taking out the scientists and other employees encountered along the way.
Soon, the three reach their destination. After convincing a scientist to open the lab door, Michael is able to grab the chemical weapon. An alarm is triggered and armed security guards begin to appear. Michael and the two FIB agents push through to the lab's garage area (Michael is now encouraged to use his regular arsenal). Outside is a refrigeration unit meant to transport the chemical weapon; Michael places the weapon in this container.
The player is shifted to Trevor flying the Jetsam Cargobob Steve purchased with the money taken in The Paleto Score. Trevor lowers the Cargobob over the refrigeration unit. However, Haines suddenly insists that the heat is too great and that they call off the operation. Michael argues and Haines soon relents. He runs back into the lab's garage and shoots himself in the leg, presenting himself as a hero to the arriving security agents. However, the United Liberty Paper Contact does not buy it and orders Haines to be detained.
With refrigeration unit in tow, Trevor flies to Sandy Shores Airfield, lowers the container onto a waiting Flatbed, then lands the helicopter. Franklin and Michael confer with Dave, who then leaves with the semitruck. After Dave is gone, Michael checks his phone and sees that Martin Madrazo has accepted Michael's peace offering (the artifact Michael and Trevor stole in the mission Derailed). Michael celebrates with Franklin, excited that he can finally return to Los Santos.
The player is shifted to Trevor as he drives Patricia back to her husband. The radio in Trevor's Bodhi is automatically set to Los Santos Rock Radio, with "If You Leave Me Now" by Chicago setting the appropriate mood. As they drive, Patricia tells the crying Trevor that she will miss him but that this is for the best. Trevor leaves Patricia at Madrazo's ranch, but not before threatening a clearly frightened Martin. Patricia heads inside the house and Trevor drives off. At this point, the mission ends.
- Navigate down to the coast line. - (Michael)
- Gain entry to the lab. - (Michael)
- Go to the elevator. - (Michael)
- Incapacitate the lab workers. - (Michael)
- Take cover from the security guards. - (Michael)
- Get the nerve toxin. - (Michael)
- Take out the security guards. - (Michael)
- Put the nerve toxin into the refrigeration unit. - (Michael)
- Collect the container. - (Trevor)
- Fly to the airfield. - (Trevor)
- Land the crate on the trailer. - (Trevor)
- Land the helicopter. - (Trevor)
- Drive Patricia to the farm house. - (Trevor)
Gold Medal Objectives
- Stunner - Stun 8 enemies with the Stun Gun.
- Self explanatory, however, the player may need to stun one of the first guards after retrieving the neurotoxin.
- Headshots - Kill 15 enemies with a headshot.
- Accuracy - Finish with a shooting accuracy of at least 70%.
- Kill as many enemies with a headshot. This helps with the accuracy achievement.
- Time - Complete within 13:30.
- Skip all cutscenes.
- Completing the mission removes the restriction on Trevor and Michael re-entering Los Santos, as Madrazo has accepted their peace offering and thus permanently called off the hit against them.
- Michael's mansion is reactivated as a safehouse. However, entering Floyd's Apartment will trigger the Hang Ten mission, and any vehicles parked in the driveway will no longer be there. Trevor's Trailer continues to be a safehouse for Trevor, but can no longer be accessed by Michael for this purpose.
- After this mission, Michael's default vehicle once again becomes the Tailgater. However (as indicated in an e-mail Michael receives from Jimmy) the vehicle has now undergone extensive modifications and as such is a more powerful vehicle than before. It has also been modified, with dollar wheels, window tints and bumper upgrades. Any respray will be undone and the car will retain its original black color. You can still customize the car as much as you please and it will retain all changes when switching to Michael. Michael's red Premier will no longer be available.
- Trevor will receive a brief phone call from Patricia soon after she is dropped off.
- Michael can phone Solomon Richards to inform him that he is back in Los Santos.
- Everything that was in boxes at Franklin's Vinewood House will be unpacked and on display in various areas. A laptop computer will now spawn on the kitchen table and can be used regularly.
Weazel News Newspaper
"A violent break in at a biotech lab in the San Chianski Mountains ended in bloodshed, mayhem and the loss of a formula for cheap perfume. The meticulously planned raid appears to have been carried out by highly skilled professionals, as thieves swam into the facility using diving equipment to access an underwater drainage pipe. Several research scientists and security personnel were killed at the facility which has been attacked by animal welfare activists in the past. The facility was once believed to have been a testing center for chemical and biological weapons, but those rumors have long been dispelled and now the facility tests soaps, high tech face creams and cosmetics. Agents are baffled as to the scale of the raid, as the perfume formula stolen was not considered particularly valuable."
Weazel News (Radio)
"Industrial espionage in Blaine County as thieves steal perfume formula. Some highly trained thieves raided a research lab yesterday in order to steal perfume. Several men were killed as raiders carried out an audicious attack that has confused the lab's owners and criminal investigators as the robbers escaped with a new formula for cheap perfume and no one is quite sure why."
- Tracey De Santa - "Hope you're taking care of yourself, Dad. I know what a magnet for absolute chaos you are."
- Amanda De Santa - "I hope none of this stuff I'm seeing on the news has anything to do with you."
- Tracey De Santa - "If it makes you feel any better, Fabien is a real douchelord."
- Rarely, a glitch can occur whereby after the player reaches the surface of the water and tries to climb the ladder, Michael will automatically slide down the ladder every time making it impossible to progress the mission. The only way to fix this is to reload a previous save, as it is impossible to fail the mission at this stage.
- Players trying to start this mission will frequently be met by a message saying "This mission has been disrupted". This is because the method used to approach the start of this mission must be correct. To avoid this, the player can choose the skip trip option.
- Sometimes, when replaying the mission, there's a chance that, upon getting to the exit of the facility, prior to entering the Cargobob, every NPC will stop shooting, preventing the mission from progressing.
- This mission is directly connected to the GTA Online Heist finale The Humane Labs Raid. It also explains how Haines finds out, through what he only describes as his "sources", that the facility is making a nerve toxin.
- There was originally a helicopter chase through the city in the beta, similar to The Merryweather Heist (offshore approach).
- If the player fails the mission by spooking Madrazo's men, the mission fail message will incorrectly spell Madrazo as "Madrazzo".
- Despite Steve Haines saying that this was a six-man job, it was completed with only four (Franklin only handled organizing the getaway).
- The Jetsam Cargobob can be obtained in this mission and stored in the player's Helipad. The Jetsam edition of the Cargobob is rare in story mode, because the chopper is in white and red, while the standard Cargobob only comes in two variants: Camo, and black. It also doesn't have the Sea Stallion (part of what the Cargobob was made from) "buff" in the front. It can be obtained by first dropping the container on the trailer, and NOT landing the Cargobob in the given location. And try to shove the Frogger (or any other helicopters that may be stored there) off the helipad, but be warned it may explode. After the Frogger is off the helipad, land the Jetsam Cargobob, and commit suicide (as Trevor). When the game asks to replay this mission, select no, and then when the player regains control of Trevor, RUN to the Sandy Shores air field (do not drive or take a cab) and the chopper should still be there and can be saved on the helipad, provided the player doesn't change helicopters, or the Jetsam Cargobob will disappear.
- Alternatively, instead of shoving the Frogger off the helipad, the player can land the Jetsam Cargobob near the player's Helipad, and then exit the Cargobob. A warning message will appear telling the player to return to the Cargobob and resume the mission, but ignoring this warning will not cause the mission to fail. The player can walk to the helipad, enter the Frogger (or any other helicopters that may be stored there), and fly and land them away from the helipad, then return back to the Cargobob, and land it safely on the now-empty helipad. After this, the Jetsam Cargobob is stored and the player (as Trevor) can commit suicide. When the game asks to replay this mission, select yes, and the player will respawn to the latest checkpoint (as Trevor again, inside the Jetsam Cargobob carrying the toxin above the Humane Labs), and the mission can be continued and finished as normally thereafter. This alternate method ensures that the player can store the Jetsam Cargobob safely without shoving other helicopters and risk any explosions, while at same time, resume the mission without restarting it.
- In the opening cutscene, Michael will tell Franklin that he has not heard from his family at all. This is not true, as Tracey will have emailed him at least once by this point, and Jimmy may have texted him right around this time telling him he has returned Michael's car.
- Starting the mission as Trevor will skip this entire conversation.
- The cooling tunnel underwater will have a secondary grate put over it after the mission to prevent the player from entering the facility again.
- This mission has several references to the Metal Gear Solid franchise:
- Michael infiltrates the research facility by entering the exhaust shaft underwater. This is a reference to how Solid Snake entered Shadow Moses island in Metal Gear Solid and how Raiden entered the Big Shell via underwater in Metal Gear Solid 2: Sons of Liberty.
- Michael cuts the grate in order to enter the labs. This is a reference to how Solid Snake cut a hole in the Big Shell's oil fence in Metal Gear Solid 2: Sons of Liberty.
- Michael is using a Stun Gun in this mission for non lethal methods. MGS franchise features tranquilizer guns used by the player to put enemies to sleep in order to not kill them. Dave Norton also says "Put the humanitarians to sleep Michael", referencing to how the tranquilizer gun from the Metal Gear Solid series puts enemies to sleep.
- This mission requires an access card from a scientist to open a certain door. This is a reference to how Solid Snake and Raiden used access cards in order to open certain doors in Metal Gear Solid and Metal Gear Solid 2: Sons of Liberty.
- When Trevor and Michael talk while flying away after picking up the container, the latter will move his lips while Trevor is talking. Additionally, when Michael tells Trevor that Steve Haines shot himself, his lips don't move.
- After this mission is completed, and Patricia has returned to her home, Trevor's trailer will become dirty again, with trash scattered across the rooms, and cockroaches plaguing it once more.
- Even if the player didn't kill any scientists, the in-game news report will still state that several scientists were killed.
- Trevor receives a phone call from Haines directly before this mission to inform him that it is time to do it. If one switches to Michael directly after this phone call, he will be in Paleto Bay, giving the idol found in Derailed to Lester. If one switches to Franklin directly after the phone call, he will be on his way to the mission location, just down the road from it. Regardless, Michael will always be the first character there.