The Theft of the Mind Stone was a plan executed by the Avengers as a part of their Time Heist to acquire the Mind and Space Stones in New York City, during and after the Battle of New York. They remained unsuccessful in stealing the Space Stone, however, which prompted Iron Man and Captain America to go even further back in time to April 1970.
The Mad Titan Thanos ultimately came into possession of the Mind Stone and contained its powers in the Scepter, which he entrusted to the exiled Asgardian prince Loki along with his army of Chitauri and Leviathans to subjugate Earth. In return, Loki promised to bring the Tesseract- which contained the Space Stone- to him. However, Loki's efforts thwarted by the Avengers, who relinquished the Scepter to S.H.I.E.L.D.. However, due to the HYDRA Uprising, the Scepter was stolen and was studied at a HYDRA laboratory in Sokovia, until the Avengers secured it and created Vision as a response to the Tony Stark's creation of the rogue Ultron. Years after the Ultron Offensive and the Avengers Civil War, Thanos nevertheless invaded Earth, and ultimately killed Vision before he inserted the Mind Stone into his gauntlet before proceeding to wipe out half of the universe's population.
Five years later, the Avengers, who had discovered that they could use the Quantum Realm and Tony Stark's Time-Space GPS to travel through time and space, hatched a Time Heist, in which they would travel to the past and amass the six Infinity Stones in order to undo the Snap.
Ant-Man, Iron Man, Hulk, and Captain America were tasked with going back in time to May 4, 2012, during the Battle of New York, to retrieve the Mind Stone, Space Stone, and Time Stone as half of the six Infinity Stones were in New York City on that day. Captain America was tasked with securing the Scepter from HYDRA.
During the aftermath of the Battle of New York, Tony Stark notices the 2012 Avengers gathered in Stark Tower, as they are preparing to meet with the "STRIKE agents" to hand them the Scepter. Stark alarms Rogers that his cue is coming, and Rogers says he is en route via elevator. Stark quietly infiltrates the building as he eavesdrops on the 2012 Avengers with 2012 Loki. Stark makes a snarky remark to Rogers that his old suit did nothing for his ass, leaving Lang to joke that that is "America's ass." Stark quietly watches as the STRIKE team arrives and 2012 Black Widow hands them the Scepter. As the STRIKE agents secure the Scepter, Lang asks who they are, and Stark answers that they are HYDRA agents posing as S.H.I.E.L.D. agents, however at this particular point in time the Avengers were not aware of this. As the agents and the Avengers separate, Lang and Stark plan on securing the Tesseract as Stark flies outside, informing Rogers that the agents with the Scepter are on the elevator passing the eightieth floor.
Rogers copies and tells Stark they will rendezvous in the lobby, as he prepares to enter the elevator with the agents, posing as his 2012 counterpart. Rogers enters the elevator, Jasper Sitwell questions Rogers for abandoning his search and rescue mission, prompting Rogers to answer that there was a change in plans. Rogers and Brock Rumlow awkwardly greet each other. Rogers tells the group that the secretary ordered him to take point on the Scepter, as there may be an attempt to steal it; however, Sitwell and Rumlow are skeptical and refuse to hand the Scepter over. Rogers earns their trust by whispering "Hail HYDRA" in Sitwell's ear, successfully leaving the elevator with the Scepter.
As conflict arises and Lang and Stark fail their mission to retrieve the Tesseract, Rogers asks them what is going on but they do not answer. Rogers then finds himself confronting his 2012 counterpart, who believes he is facing Loki transformed into himself. Present Rogers says he is not Loki and wishes not to hurt his past self, but past Rogers quickly goes on the attack. The two fight an even match until they both fall to the floor below, as past Rogers notices present Rogers' discarded locket with Peggy Carter's picture.
Past Rogers asks present Rogers where he got it, but locks present Rogers in a headlock as he tries to secure the Scepter. Thinking quickly to save himself, present Rogers tells his counterpart that Bucky Barnes is alive, prompting the past Rogers to let his guard down in confusion, only to be knocked unconscious as present Rogers uses the Scepter on him. As present Rogers secures Peggy's locket and the Scepter, he confirms to himself that that is "America's ass" as he makes his way to the lobby.
Captain America successfully escapes from Stark Tower with the Scepter and makes his way to the alley, where he discovers that Iron Man and Ant-Man failed in their mission to acquire the Tesseract. Only possessing enough Pym Particles on hand for a single trip, Stark offers an alternate plan, claiming that in April 1970, both the Tesseract and Pym Particles were housed at Camp Lehigh in New Jersey. As Stark and Rogers prepare to go on their new heist, Rogers hands over the Scepter to Lang, informing the new Avenger to bring it to the New Avengers Facility.
The Mind Stone was extracted from the Scepter and placed within the Nano Gauntlet, created by Stark, Hulk and Rocket Raccoon. Following the Battle of Earth, the Mind Stone was placed in a suitcase and given to Rogers, who traveled back in time once again to return the stone, albeit without the Scepter.