Fallout 4's main story revolves around the protagonist's missing son, four warring factions with their own views on the future of the Commonwealth, and the existence of synths, artifical people. Synths are made by the Institute, intended as an expendable workforce of near-perfect human copies. But the synths have wants of their own, leading to many of them defecting and running away. Despite the complexity of the synth's own mindsets, most people in the wasteland view them as abominations, and seek to eradicate them.

The most powerful force seeking to destroy synths is the Brotherhood of Steel, and if the player chooses to work with this organization, they'll meet Paladin Danse, a committed Brotherhood soldier who is fully on board with wiping out the synths. That is, until he learns that he himself is in fact a synth, one that defected and had its previous memories wiped. But one mystery the game never clearly answers is this: when exactly was Paladin Danse replaced with a synth?

Danse Is Confirmed To Be A Synth During The Brotherhood Questline

A Man Confronted With His Own Humanity

While many NPCs in Fallout 4 are in fact secret synths, there aren't many hints at Danse's true identity early on. He is a loyal member of the Brotherhood, slaying super mutants and synths without question, acting solely for the organization's benefit. It makes the revelation of his true nature all the more troubling for the player and himself, and may even drive Danse to asking the player to kill him.

The Brotherhood itself confirms that Danse matches with a synth the Institute flagged as "missing," and if killed, he drops a synth component.

Following this, the player may still convince Danse to keep living, and even convince Elder Maxson to spare the former Paladin. If so, he'll keep living at Listening Post Bravo, and will still be available as a follower. But the exact reason for Danse's defection from the Institute is never given, nor is it confirmed when the swap took place. Danse has memories of his childhood, but the Institute is known to be able to replicate whole lives in the heads of their creations, so nothing Danse knows can help reveal the truth.

Paladin Danse Could Have Been A Synth Since He ed The BoS

An Infiltrator Since The Beginning

It's entirely possible, given what we know about Danse and the Fallout universe, that he has been a synth since before he even ed the Brotherhood. According to his childhood memories, Danse grew up in Rivet City, and ed the BoS with his friend Cutler when they were both still young. Rivet City is the location of another known runaway synth, Harkness, and a surgeon with the skills to alter a synth's memories and face.

This would make some sense, since it would mean that the synth which became Danse never intended to the Brotherhood, known eradicators of its own kind. But it does pose some issues, since it's not known if or how synths age, and the Institute scientist Dr. Zimmer never mentions another escaped synth while he is tracking down Harkness in Fallout 3.

Danse was a member of the Brotherhood for years before the start of the game, and could theoretically have been replaced at any point in that time.

Danse was a member of the Brotherhood for years before the start of the game, and could theoretically have been replaced at any point in that time. Though it would be very risky for a synth to emulate a Brotherhood soldier, since they'd be putting themselves directly in harm's way. It might make sense if Danse was intended as an Institute spy, but the Institute clearly considers him "missing," not on an assignment.

Danse Likely Became A Synth While Stationed In The Commonwealth

The Most Likely Explanation For This Android's Origins

The most likely explanation is that Danse was replaced during the time he was stationed in the Commonwealth, some time shortly before meeting the player. This would put Danse in proximity to the Institute itself, as well as the Railroad and Dr. Amari, who may have helped him escape and change his memories. It also coincides with some evidence found in Scribe Haylen's notes.

Danse arrived in the Commonwealth ahead of the Brotherhood's main force as the leader of a recon group, and his soldiers were slowly picked off by threats as they searched for technology to salvage. This would have been an opportune time for Danse to die (or maybe be killed) and be replaced by a synth copy. And in Haylen's notes, she observes that Danse began to experience headaches and insomnia at some point after losing some of his men, which could be a side effect of the synth's recent reconstructive surgery.

Danse's symptoms could have been psychosomatic, the result of the trauma of losing his friends, but synths are also known to experience slight behavioral changes (such as a change in sleep schedules) upon taking on a new identity that may have been perceived as insomnia.

If this was the case, and Danse was replaced while in the Commonwealth, it would mean that the "real" Danse died fairly recently, and this version of him has only been Danse for less than a year. Given how paranoid The Brotherhood of Steel are, and how quickly they discover Danse's synth nature once the Prydwen arrives, it's likely that he couldn't have hid among their ranks for much more time than that. This is by no means confirmed, but it seems to be the most likely timetable for Danse's synth transformation in Fallout 4.