Mysterious Stranger (character)

The Mysterious Stranger is the individual that may appear if the player character has the Mysterious Stranger perk. They lend a helping hand in battles.

Background
The Mysterious Stranger in Fallout 3 and Fallout: New Vegas is heavily implied to be the father of The Lonesome Drifter. In speech, the Drifter will state that his father was a "mysterious" man, and that he was a "stranger" to his own family. The word mysterious appears right above stranger in the dialogue box. His name appears to be inspired by the Mark Twain Story No.44 The Mysterious Stranger which would be why The Drifter carries a unique .44 Magnum, which can be acquired by the Courier, that looks remarkably like the Mysterious Stranger's .44 Magnum; and when drawing it, the same guitar notes that are heard when the Mysterious Stranger shows up are played, and a chord is played when the weapon is holstered. As of Fallout 4, the Mysterious Stranger is currently being investigated by Nick Valentine, who has made note of his several appearances in other games of the series, and attempts to apprehend him when he appears.

Other interactions
There is a chance that Mysterious Stranger will appear as a temporary ally during random encounters.
 * $$\text{Chance of appearance }%=30+(2\times\text{Luck})$$

Other interactions
The Mysterious Stranger will appear out of nowhere to assist in battle by finishing off enemies. After the V.A.T.S. sequence finishes, he will disappear in a similarly abrupt manner.

Fallout Shelter
The Mysterious Stranger appears in vault rooms or elevators. He does not aid in battles, but may appear in the vault regardless of if the vault is experiencing an incident. When selected, he disappears and the vault is awarded a random amount of caps. He must be tapped on to receive the caps. If any rooms are not powered he will not appear, even when the sound effect occurs. Finding him two, four, and five times, respectively, are three of the objectives. He can spawn at anytime, appears with a smoke poof and leaves with one as well. He will spawn in intervals of at least 10 minutes.

Fallout 3, Fallout: New Vegas

 * A short guitar riff will play whenever the Stranger holsters or unholsters his weapon, as does the Mysterious Magnum.
 * He circles around the enemy shooting several times.
 * He can appear in water, and swim around. He will not shoot when this occurs.
 * In Fallout 3 and Fallout: New Vegas, The Mysterious Stranger has a unique .44 Magnum; Mysterious Stranger's .44 magnum that can only be obtained via console commands. It deals up to 9000 damage, making it one of the strongest weapons in both games.

Fallout 3
During the add-on Mothership Zeta, having the Mysterious Stranger perk opens up a unique dialogue option with Somah. "Maybe, if we're lucky, a friend of mine will show up to help us," to which she responds with confusion.

Fallout: New Vegas
He may have a son, The Lonesome Drifter, who wanders around the wasteland looking for his father.

Fallout 4

 * Unlike Fallout 3 and Fallout: New Vegas, The Mysterious Stranger no longer appears to be Asian. He now also sports a mustache, appears older, and has his coat buttoned shut rather than being tied shut. His outfit is also no longer unique to him, and can be found in the wasteland.
 * The Mysterious Stranger isn't bearing a Mysterious Stranger's .44 magnum as he did before in Fallout 3 and Fallout: New Vegas. Instead he uses the standard issue .44 Magnum and possesses a special and unique perk, named "Mysterious Stranger Damage", which increases all the damage stats on all weapons except melee weapons. It can be obtained only through console commands using.
 * The riff alerting to his upcoming presence is considerably different to previous games.
 * Nick Valentine is trying to learn about the Mysterious Stranger. Nick has a short log containing everything he knows about the Stranger in his office, and if the player character has Nick as a companion while the Stranger appears, Nick will exclaim in frustration as the Stranger slips away.

Fallout 76
The mysterious stranger is the only "human" in Appalachia to survive the Scorched Plague.

Appearances
The Mysterious Stranger appears in Fallout, Fallout 2, Fallout 3 and all its add-ons, Fallout: New Vegas and all its add-ons, Fallout 4 and all its add-ons, and Fallout 76, making him the only character to appear in all canon Fallout games. He also appears in Fallout Shelter.

Behind the scenes
The Mysterious Stranger is a reference to the unfinished Mark Twain Story No.44 The Mysterious Stranger. The Mysterious Stranger is inspired by the trenchcoat-clad figures of 1940s and 1950s film noir.

Fallout 3, Fallout: New Vegas

 * If the Mysterious Stranger appears and there is a wall or other obstacle between him and his target, he will not take a shot. This will sometimes lead to you being stuck in V.A.T.S. permanently, necessitating a reload of an earlier save.
 * This may also happen if your target is swimming as he will not be able to draw his weapon and will swim around possibly rendering you stuck in V.A.T.S.
 * If the enemy is near a cliff and a weapon is used that knocks them off it without killing them, the Stranger may spawn in the air off the cliff and fall to his "death" as a result. As he is an "essential" character he will be rendered unconscious and the "Mysterious Stranger is unconscious" message will appear on screen like any other essential non-player character. This will not prevent him from appearing to aid the player at a later date.
 * You can sometimes knock the Mysterious Stranger unconscious if you attack a nearby enemy in V.A.T.S. with an explosive such as a grenade.
 * After the Mysterious Stranger has killed his target, there may be a considerable delay in V.A.T.S. before he goes away and normal play is resumed. You and companions can still be attacked and may be killed if there are other enemies around.

Fallout 4

 * If the Mysterious Stranger appears and there is a wall or other obstacle between him and his target, he will not take a shot.
 * The Mysterious Stranger spawns either on top of the enemy or within touching distance and won't fire his shot. He continues doing this and resetting the game doesn't fix it, effectively making him useless.
 * If this happens try to put space between you and your target

Sounds
Mysterious Stranger appearing in Fallout 3 and Fallout: New Vegas Mysterious Stranger appearing in Fallout 4

Mysterious Stranger appearing in Fallout Shelter

Gallery
Mystérieux Etranger (Personnage) Таинственный незнакомец (персонаж) Таємничий незнайомець (персонаж)