Time Heist

"Six stones, three teams, one shot. Five years ago, we lost. All of us. We lost friends. We lost family. We lost a part of ourselves. Today, we have a chance to take it all back. You know your teams. You know your missions. Get the stones. Get them back."

- Captain America to the Avengers The Time Heist was a planned mission organized by the Avengers, aimed at resurrecting the victims of the Snap by going back in time and retrieving the Infinity Stones from alternate timelines, resulting in the final battle against an alternate Thanos and his army.

Ambush on Thanos
"We get the stones. We use them to bring everyone back."

- Captain Marvel In 2018, the Avengers, Captain Marvel, and Nebula travelled in the Benatar to Planet 0259-S to retrieve the Infinity Stones from Thanos. When they arrived, they found a heavily crippled Thanos, who had destroyed the Infinity Stones to keep his work intact. After realizing there was no way to bring back the vanished, Thor decapitated Thanos and the Avengers returned to Earth, completely defeated.

Scott Lang's Return
"What if there was a way to enter the Quantum Realm at a certain point in time but then exit at another point in time? Like... like before Thanos."

- Scott Lang By 2023, Tony Stark had retired, married Pepper Potts, and had a daughter, Steve Rogers had engaged in therapy sessions, and Natasha Romanoff continued to command the Avengers with Rocket Raccoon, James Rhodes, Carol Danvers, and Okoye. In a San Francisco warehouse, a rat accidentally walked over the controls of the Quantum Tunnel, which was housed in Luis' van, and released Scott Lang from the Quantum Realm. Lang then reunited with his daughter and went to the Avengers Compound to meet with the Avengers. Once there, Lang discussed the Quantum Realm with Rogers and Romanoff, explaining the physics behind the Realm and how five years had passed for the Avengers while it was only five hours for him. With that in mind, Lang suggested using the Realm to go back in time to prevent the Snap from occurring.

Planning the Heist
"A time heist. Of course. Why didn't we think of this before? Oh, because it's laughable? It's a pipe dream?" "The stones are in the past. We could go back, we could get them." "We could snap our own fingers. We could bring everyone back."

- Tony Stark, Steve Rogers and Natasha Romanoff Steve Rogers, Natasha Romanoff, and Scott Lang went to Tony Stark for assistance but Stark turned them down, having moved on and not wanting to risk his daughter's life. With Stark refusing to help, Bruce Banner was contacted by them to see if he could help, before Banner revealed his new condition to the three.After some persuasion, Banner returned to the Avengers Compound and attempted to run some tests on Lang by letting him go through the Quantum Realm which proved to be ineffective due to sending time through Lang instead of sending Lang through time. Not long after, Stark returned to the Facility, agreeing to help them if they would restore the Snap's victims to the present day rather than undoing the Snap, as he did not want to lose his daughter. With Rogers agreeing, Stark presented the Avengers with the newly invented Time-Space GPS which allowed for safe and accurate traveling through the Quantum Realm to reach different time periods. After a test run on Clint Barton, who was brought in by Romanoff, proved successful, the Avengers planned the many possibilities in a session, concluding which points in time would be most effective to reclaim the Infinity Stones.With Stark and Rocket Raccoon's help, the Avengers created a new Quantum Tunnel and Advanced Tech Suits as they planned out their heist, deciding to split into three groups to search for the different Stones. Lang, however, warned that due to the short supply of Pym Particles, they could only make one round trip each and thus there was no room for any mistakes.

Theft of the Mind Stone
"Sorry, Cap. We can't give you the Scepter." "I'm going to have to call the Director." "That's okay. Trust me. Hail HYDRA."

- Brock Rumlow, Jasper Sitwell and Captain America As the Mind Stone was in the Scepter that Loki used during the events of the Battle of New York, Iron Man, Captain America, and Ant-Man went back in time to an alternate 2012. The Avengers set out to retrieve it and the Tesseract which contained the Space Stone as well. The Scepter was retrieved by Captain America at Stark Tower from Jasper Sitwell and Brock Rumlow after uttering "Hail HYDRA" to Sitwell, which was more than enough to convince them to give him the case with the Scepter, leaving them stunned.

Theft of the Time Stone
"I'm sorry, I can't help you, Bruce. If I give you the Time Stone to help your reality, I'm dooming my own."

- Ancient One to Bruce Banner Aware that the Time Stone was in possession of the Masters of the Mystic Arts, Bruce Banner arrived at the New York Sanctum and met the Ancient One. Banner, however, was unaware that Doctor Strange was still a practicing surgeon at that time. The Ancient One caught on to the current state of affairs and initially refused to give the Stone to Banner, fearing that her new reality may be defenseless without the Time Stone and that the Masters of the Mystic Arts swore to protect the Stone with their lives and giving it to him would break the oath. Banner then told her that Strange already broke the oath when he gave the Time Stone to Thanos. Knowing that Strange would only do this if he genuinely had no choice, she eventually gave it to Banner who promised that all the stones would be returned to their proper places in time afterward and that they would survive the ordeal.

Theft of the Space Stone
"I got it. There's another way to retake the Tesseract and acquire new Particles. A little stroll down memory lane. Military installation, Garden State."

- Tony Stark to Steve Rogers Ant-Man was tasked with incapacitating the alternate Iron Man so that Iron Man could get the case with the Tesseract. Ant-Man shrunk inside the alternate Iron Man's Arc Reactor in order to sabotage the device, which caused him to endure a mild heart attack. Ant-Man then kicked the suitcase to Iron Man, who was disguised as a security guard. As he was about to take the case, the alternate Hulk came crashing through the stairwell, angered about using the stairs to go down instead of the elevator, and bumped into Iron Man. The case then slid across the floor and landed at alternate Loki's feet, who used the Tesseract to teleport away. When Iron Man and Ant-Man met up with Captain America and explained their failure, Iron Man proposed the idea to go back to Camp Lehigh in an alternate 1970 where the Tesseract, as well as extra Pym Particles, were kept. Iron Man and Captain America then proceeded to travel to that timeline.

Theft of the Reality Stone
"Here's the deal, tubby. You're gonna charm her and I'm gonna poke her with this thing and extract the Reality Stone and get gone lickety-split."

- Rocket Raccoon to Thor Thor and Rocket Raccoon arrived in an alternate 2013 Asgard on the day the Dark Elves attacked. Thor quickly lost his composure at the sight of his old home, and while Rocket did his best to keep him focused, Thor was distracted by the sight of his mother, who died the same day, forcing Rocket to get the Reality Stone from Jane Foster himself. After sneaking into her room and extracting it, he was chased by the Einherjar. Rocket eventually met up with Thor and Frigga, who had been talking outside. Before they went back to their timeline, Thor was able to summon Mjølnir to him, happy that he was still worthy.

Theft of the Power Stone
"We just wait around for this Quill guy to show up and then he leads us to the Power Stone."

- War Machine to Nebula On Morag in an alternate 2014, War Machine and Nebula waited for the alternate Star-Lord, who would steal the Orb containing the Power Stone, to arrive. The two then trailed Star-Lord, who War Machine stated that he was an idiot. War Machine then knocked out Star-Lord and Nebula stole the tool that Star-Lord would use to gain access to the room containing the Orb. Nebula then used her cybernetic arm to get the Orb. War Machine then took the Orb and returned to their timeline.

Kidnapping of Nebula
"Barton, come in. Romanoff, come in, we have a problem. Come in, we have a prob– Thanos knows."

- Nebula The 2014 version of Nebula was on a mission with the 2014 version of Gamora when Thanos summoned them to debrief them on their mission to retrieve the Power Stone with Ronan the Accuser. However, Nebula began feeling pain and began playing a memory from the future Nebula which prompted Thanos to bring them to a room with Ebony Maw, where he revealed that the implants in both Nebulas were interacting with each other which allowed both to access the others' memory files. This allowed Thanos to see the future where he ends up being decapitated by Thor. Thanos stopped Ebony Maw from killing Nebula as he discovered a way to accelerate his plans. Nebula on Morag also saw a memory file of her past self, alerting her that Thanos was now aware of the Avengers' plan and rushed to the Benatar’s pod to contact Hawkeye and Black Widow to warn them, but was captured. The 2014 Nebula then stole the Advanced Tech Suit and disguised herself as the present Nebula and went to the future in order to help bring Thanos and his army to 2023.

Sacrifice of Natasha Romanoff
"She sacrificed her life for that goddamn stone, she bet her life on it."

- Hawkeye Hawkeye and Black Widow arrived on Vormir where they met Red Skull and were told about the stone requiring a sacrifice. The two spent time on the edge debating on who should be the one to die. Hawkeye volunteered, asking Romanoff to tell his family that he loves them. Instead, Romanoff attacked Barton, telling him to say it himself before rushing off to the edge. Hawkeye then chased her down and the two have a scuffle. When Barton emerged victorious, he flung himself off the cliff, but Romanoff jumped on him, and then they both fell off the cliff with Barton using a grapple to hang on to while holding on to Natasha. She then allowed herself to fall to her death. The sky lit up and Barton woke up in a pool of water with the Soul Stone in his hand and then made his way back to his timeline.

Aftermath
"We tampered with the stability of space-time to resurrect countless lives."

- Doctor Strange to Peter Parker Everyone, sans 2023 Nebula, who was subdued and impersonated by her 2014 self, and Natasha Romanoff, arrived back at the facility, where they all celebrated their victory. However, this was cut short, when Clint Barton fell to his knees, causing everyone to see that Romanoff was not there, realizing that she had died during the mission. The original Avengers gathered outside to mourn their friend, where Barton made it clear that Romanoff could not be brought back. They all then made a promise to not let their friend's death go meaningless, so they started working on controlling the Infinity Stones to resurrect the victims of the Snap. Doctor Strange would later express concerns regarding the impact that the Time Heist had on the space-time continuum and how it affected the Multiverse on a whole.

Blip
"Okay, remember, everyone Thanos snapped away five years ago, you’re just bringing them back to now, today. Don't change anything from the last five years."

- Tony Stark to Bruce Banner They proceeded to create the Nano Gauntlet that could harness the power of the Stones. Thor volunteered to wield the gauntlet, but was turned down due to his unstable state. Bruce Banner informed them that he had to do it, stating that the Stones emitted Gamma Radiation, so he would be the one with the best chance to survive it. Everyone then suited up and braced themselves in the event that something went awry, with Stark putting the Avengers Compound on lockdown. Meanwhile, the alternate Nebula used the Quantum Tunnel to bring an alternate Thanos and his ship to the timeline, crashing through the hangar and taking its place in the sky above the Facility.The Avengers were too occupied to notice the commotion. After some difficulty containing the gauntlet's power, Banner said that he was okay and was able to snap his fingers, restoring every victim of the Snap. They realized it worked when Hawkeye got a call from his wife and Ant-Man noticed birds on a tree that were not there before. However, this was cut short, when the Facility was destroyed by alternate Thanos' ship, causing the Avengers to be separated: Hawkeye landing underground with the gauntlet, War Machine, Banner, and Rocket Raccoon trapped underneath rubble, and Iron Man, Captain America, and Thor on the main level, confronting Thanos.

Trivia

 * According to Ravonna Renslayer, the Avengers going back in time was meant to happen, or was an event "approved" by He Who Remains not to be considered a Nexus event, and thus the Time Variance Authority never went after them for changing the past. However, this did indirectly cause a Nexus event in the form of alternate Loki escaping with the Tesseract.