Fallout 4 takes place in the year 2287, ten years after the events of Fallout 3 and 210 years after a Resource War over natural resources that ended in a nuclear holocaust in 2077. The setting is a post-apocalyptic retro-future, covering a region that includes Boston, Massachusetts and other parts of New England known as "The Commonwealth". Unlike the previous titles, Fallout 4's story begins on the day the bombs dropped: October 23, 2077. The player's character (voiced by either Brian T. Delaney or Courtenay Taylor) takes shelter in Vault 111, emerging exactly 210 years later, on October 23, 2287. The game takes place in an alternate version of history that sees the 1940s' and 1950s' aesthetics, design and technology advance in the directions imagined at the time. The resulting universe is thus a retro-futuristic one, where the technology has evolved enough to produce laser weapons, manipulate genes and create nearly-autonomous artificial intelligence, but all within the confines of 1950s' solutions like the widespread use of atomic power and vacuum tubes, as well as having the integrated circuitry of the digital age. The architecture, advertisements and general living styles are also depicted to be largely unchanged since the 1950s, while including contemporary products, such as a robotic rocking horse for children in one advertisement, or posters for the underground vaults that play a central role in the storyline of the game.

      The story begins on the morning of October 23, 2077 in Sanctuary Hills, with the player character, their spouse (Nate/Nora), their son Shaun, and their robotic butler, Codsworth. As the player character is preparing for an event at the Veteran's Hall in Cambridge, a representative from Vault-Tec comes to inform them that their family is approved for admittance into Vault 111, the local fallout shelter. Moments later, a news bulletin warns of an imminent nuclear attack. This forces the family into rushing to the Vault, where they are temporarily trapped outside when a nuclear bomb detonates nearby. The platform then lowers them just in time before the shockwave from the nuclear blast arrives, saving the family and other Sanctuary Hills residents that made it to the platform. Unfortunately, upon entering the Vault, the player character and family are tricked into entering cryogenic tubes by the Vault-Tec staff and frozen alive. After an unknown period of time, the player character and their spouse are re-awakened by two unknown individuals. They open the spouse's cryo-tube with the intent of taking the player's baby, Shaun. When the spouse tries to prevent the kidnapping, they are killed by one of the strangers, who takes Shaun and reactivates the player character's cryo-tube. The player character manages to get free of their cryo-tube at some point later, upon which they discover that they are the sole survivor of Vault 111. On emerging from the vault, the Sole Survivor vows to avenge their spouse's death and find Shaun. The player character heads home to Sanctuary Hills which is now ruined from the bomb blast. The Sole Survivor meets a distraught Codsworth, revealing to the Survivor that over 210 years have passed since they were frozen in the Vault. Codsworth informs the player character to go to Concord for help. On their way there, the Survivor meets a stray dog, later revealed to be named Dogmeat. The Sole Survivor then meets Preston Garvey � one of the last of the Commonwealth Minutemen � and assists him in protecting settlers from a group of raiders. After assisting Garvey and his group, the player is instructed to go to Diamond City, a settlement based in Fenway Park where they meet Piper, the City's reporter, who tells the player character to seek out Nick Valentine, revealed to have been missing two weeks prior to the Sole Survivor's arrival in Diamond City. After finding Valentine � revealed to be a second-generation synth, a sophisticated biomechanical android � they learn the identity of their spouse's killer, a man named Conrad Kellogg. They later learn his location in Fort Hagen with the help of Dogmeat. After entering the fort and battling the Institute synths to get to Kellogg, he reveals that Shaun is in the Institute, a secretive organization feared by the people of the Commonwealth � that is based below the ruins of the Commonwealth Institute of Technology. After killing Kellogg, the player then retrieves a cybernetic implant from his brain, and after consultation with Nick and Piper, they head to Goodneighbor and get help from Doctor Amari � a scientist skilled in neuroscience � who can assist the Sole Survivor in viewing the dead mercenary's memories. During their hunt for Kellogg, the Survivor witnesses the Brotherhood of Steel arriving in full force with the Prydwen, their mobile airship HQ. After viewing Kellogg's memories, the player is then tasked to go to the Glowing Sea � the ground zero of the nuclear blast shown early in the game � to find Brian Virgil, an ex-Institute scientist to get help in infiltrating the shadowy organization. Brian Virgil, now mutated into a Super Mutant by FEV exposure, mentions that the player must kill an Institute Courser � one of the Institute's most advanced creations that was designed to be stronger, faster and smarter than average human beings � and get its chip, as the Institute is underground, thus the only method for travelling to and from is a teleporter. Afterwards, the player proceeds to the Railroad, named for the historical Underground Railroad, for Tinker Tom to decode the chip and get the frequency code. The player then heads back to Brian Virgil, who gives the player character a blueprint of a device that hijacks the frequency of the Institute's Molecular Relay. After retrieving the blueprints, the player seeks assistance from one of three other factions: the Minutemen, the Railroad, or the Brotherhood of Steel. Once the device is built, the player infiltrates the Institute to find their son. After finding a child synth based on a young Shaun, it is revealed that the real Shaun was kidnapped in 2227 � sixty years prior to the Sole Survivor's release from cryogenic sleep � and is now an old man, nicknamed Father, and the leader of the Institute. Shaun also reveals that he was kidnapped because of the Institute's need to find DNA unaltered by the radiation brought by the nuclear bombs so as to create the perfect synths � the fully self-aware third-generation synthetics, thus giving Shaun his moniker as Father. It was later detailed that in the Institute's search for unaltered DNA, they found records of Vault 111 showing the Sole Survivor's family � the player character, their spouse, and their son Shaun � being cryogenically frozen. Shaun also reveals that he is dying because he is diagnosed with cancer, and he plans on making the Sole Survivor the next director of the Institute. The player then faces a choice to determine the future of the Commonwealth. They can side with Shaun by siding with the Institute: The Institute � Siding with the Institute will lead the Sole Survivor to initiate a purge in the Commonwealth � wiping out the Railroad and Brotherhood of Steel (The Minutemen will be spared after passing a few speech checks). Afterwards, the player must handle internal issues within the Institute � which was caused by Father's announcement on making the Sole Survivor the next director of the organization. Or they can go against Shaun by siding with one of three other factions: The Brotherhood of Steel � Siding with the Brotherhood of Steel will lead the Sole Survivor to rebuild Liberty Prime � spearheaded by proctor Ingram � to be used as a weapon to destroy the Institute. The player's first task is to recruit Dr. Madison Li from the Institute to work on the project. Afterwards, the player must go to the Sentinel Site in the Glowing Sea to retrieve a payload of compressed nuclear bombs. Finally, the player must retrieve an advanced fusion core from the Mass Fusion building. The player is then ordered to head to the Railroad HQ and wipe the shadow organization out because they present a tactical threat to the Brotherhood. After reactivating Liberty Prime, the Brotherhood of Steel leads a charge against the Institute. The Railroad � Siding with the Railroad will lead the Sole Survivor to go undercover in the Institute and meet with a man codenamed Patriot, to devise a plan to free all the synths and destroy the Institute. The Railroad also deems the Brotherhood of Steel a threat to the freed synths and devises a plan coded "Red Rockets Glare" � a plan to bring down the Prydwen and destroy the Brotherhood of Steel in the Commonwealth. The Minutemen � Siding with the Minutemen will lead the Sole Survivor to rebuild the Minutemen in order to create an army to fight the Institute. The player is first promoted by Preston Garvey to be the General of the Minutemen and is then told to retake the Castle � the former headquarters of the Minutemen � from a Mirelurk Hive to let the Commonwealth know that the Minutemen are back. Afterwards, Ronnie Shaw � a veteran Minuteman � tells the player to retrieve plans to artillery units which will help the Minutemen maintain order against large threats in the Commonwealth. Once the Minutemen is reformed, the player is then tasked to bring the battle to the Institute (And the Brotherhood of Steel if they are hostile) in order to protect the Commonwealth. At the very end, the synth child Shaun reveals himself to his 'parent' � the Sole Survivor � and asks them if he can go live with them anywhere in the Commonwealth to be a family. If brought with, the synth child gives the player character a holotape from the real Shaun with a message that differs depending if the player sides with the Institute or not. Listening to the holotape, the real Shaun tells his parent that he wishes for them to give the synth child a chance to live as a family as Shaun himself never had the chance to with the Sole Survivor. The Sole Survivor then contemplates on the events that transpired and says that "This isn't the world I wanted, but it's the one I found myself in." because they know that "War. War never changes."

      Fallout 4 sold 1.2 million copies on Steam in its first 24 hours of release. The game also sold more digital than physical copies on day one of launch. With almost 470,000 concurrent Steam players on launch day, Fallout 4 broke Grand Theft Auto V's record for having the most concurrent online players in a Steam game not developed by Valve Corporation. The game grossed $750 million in shipped sales, with the total number of units being 12 million, also in the first 24 hours.