Paladin Danse or known by is designation code M7-97 is one of the possible companions the Sole Survivor may acquire in Fallout 4 and a high ranking member of the Brotherhood of Steel located in the Commonwealth.
Background
Paladin Danse is originally a synth created by the Institute, a fact which he himself wasn't aware of. Danse had memories of growing up in Capital Wasteland (main location of Fallout 3) as an orphan. As a child, he made a dangerous living by scavenging the D.C. ruins until he could afford to open his own junk stand in Rivet City. It was around that time he befriended a man named Cutler, and together the two scraped by as traders.
When the Brotherhood of Steel began recruiting, Danse and Cutler agreed it was "the best way out of [their] nowhere lives". They joined the order, under the training of Paladin Krieg, and were successful soldiers, but roughly a year after being posted to the Prydwen, Cutler disappeared on assignment. Danse personally spearheaded a three-week search for the missing squad. Ultimately the trail led to a super mutant hive where it was revealed that Cutler's team had been killed, and Cutler himself had been exposed to the Forced Evolutionary Virus. Danse, saddened to discover his friend had been mutated, killed Cutler. The experience incited an intense hatred in Danse of most non-humans, including super mutants, ghouls, and synths.
Danse achieved the rank of Paladin while the assault on Adams Air Force Base was happening, which resulted in the fatality of his first drill sergeant. By the year 2287, he had risen to become one of Arthur Maxson's most respected officers. He was assigned a reconnaissance team and dispatched to the Commonwealth to investigate signs of the Institute's activities. However, misfortune quickly reduced the recon team to only three members. When the Sole Survivor first encounters Paladin Danse, he and what's left of his team are holed up in Cambridge Police Station, unable to proceed with their mission. Paladin Danse enlists the aid of the Sole Survivor to help him retrieve an item from the nearby ArcJet Systems complex. After their task is completed, Danse offers the Survivor the rank of Initiate in the Brotherhood of Steel, should they wish to join.
Provided the Sole Survivor enlists in the order, Danse will become a full companion following the completion of Shadow of Steel. On their journeys Danse makes it clear he believes the Institute and its synths are too dangerous to let live, and both must be eradicated for the safety of mankind. However, after the Survivor breaches The Institute's mainframe, it is revealed that Paladin Danse himself is actually an escaped synth. Danse, or unit designation M7-97, goes AWOL shortly thereafter. Elder Maxson orders the Sole Survivor to find and execute their former mentor, saying the existence of a such a creature cannot be allowed.
When found at Listening Post Bravo Danse will swear that he had no idea that he was a synth. The disgraced paladin then encourages the Survivor to carry out their orders to kill him, insisting an example should be made and that he "must be the example, not the exception." The Survivor must then choose to either execute Danse or convince him to flee the Commonwealth. Should the Sole Survivor decide not to execute Danse, he will thank the Survivor and, with Maxson's promise not to have him hunted down, remains in the Commonwealth to aid the Survivor in their mission.
