Strangers

"Out in the frontier there are people living an everyday existence and struggling to survive. You can find these Strangers out in the wilderness or in the local towns. They are marked by '?' on your map, and can be spoken to when not busy with a mission. Their tasks can be as simple as finding a friend or loved one, picking some flowers, hunting some animals, or delivering items across the dangerous frontier. Violence can often solve these problems, but think hard before letting your gun speak first. Unlike narrative missions, Stranger's tasks can be started and finished at any time. Active tasks will be tracked for you on the map. This journal will record the name of the task, as well as the objectives for each stage."

- Journal description

Strangers are special NPC characters featured in Red Dead Redemption. Unlike core gameplay missions, these side-missions can be initiated and completed at any time. Strangers will request tasks or offer opportunities to the player.

Strangers are represented on the map by a question mark "? " icon. These question mark icons only appear on the map when the player is close to their locations. Visit the question mark icon to begin dramatic, and sometimes dangerous, chains of events.

Occasionally, the player will be given a choice on how to complete the mission,  yielding either positive or negative results for the player's honor. Additionally, the successful completion of these activities will often reward players with cash.

Helping strangers, with the exception of the mission "I Know You", contributes towards 100% Completion.

Stranger Tasks
For more information on where to initiate these tasks, how to complete them, and all other details, please choose the desired one.

New Austin

 * "American Appetites" - Randall Forrester • Grace Anderson • Ralph Anderson
 * "California" - Sam Odessa
 * "Flowers for a Lady" - Billy West • Annabel West
 * "Funny Man" - Jimmy Saint
 * "I Know You" - Strange Man
 * "Jenny's Faith" - Jenny
 * "Let No Man Put Asunder" - Alma Horlick • Peter Turner • Nathan Harling • Rose Harling
 * "Lights, Camera, Action" - D.S. MacKenna • Silas Spatchcock
 * "Water and Honesty" - Andrew McAllister • Clyde Evans
 * "Who Are You to Judge?" - Jeb Blankenship • Ann Stephenson • Lucy

Nuevo Paraiso

 * "Aztec Gold" - Basilio Aguirre Olmos de la Vargas
 * "Deadalus and Son" - Charles Kinnear
 * "Eva in Peril" - Eva Cortes • Mario Alcalde
 * "Love is the Opiate" - Zhou • Juan de la Vara
 * "Poppycock" - Uriah Tollets • Juan de la Vara

West Elizabeth

 * "American Lobbyist" - Mr. Philmore in Blackwater • The Gossiper in Blackwater Bank
 * "The Prohibitionist" - Abner Forsyth • Oliver Phillips
 * "Remember My Family" - Agent Howard Sawicki • Edgar Ross • Emily Ross • Phillip Ross
 * "The Wronged Woman" - Clara LaGuerta • Harold Thornton • Elizabeth Thornton

Tips

 * Most Stranger missions ask the player to wait a couple in-game days before the next part of the mission becomes available. Instead of waiting the player can just save the game at any property/campsite and then reload that save, or an auto-save in case this feature is turned on.

Trivia

 * Several Stranger missions were cut before the game was released.
 * In one John encounters a lonely dwarf with a hatred of people. John ends up feeling sorry for him and goes searching for someone to befriend the dwarf. Eventually John encounters a large man described as a giant. However after meeting each other the giant ends up killing someone by accidentally smothering them. The dwarf then encourages John to kill the giant and the large man's fate is left in the players hands. Only the audio for this cut mission remains. https://youtu.be/mM6R2pXxmbg
 * In another John must gather four stolen holy relics for Mother Superior. The first relic is described as being in the possession of a hermit in New Austin. One was being sold in the Pacific Union Railroad Camp. The next in possession of a criminal who lives in Tumbleweed and finally one by an outlaw hunted by bounty hunters. https://youtu.be/0rBNHLYuKUM
 * Most of the stranger missions seem to be a lot of work for no good reason, or in the favor of sick, twisted, and evil needs being satisfied.

Achievements
There are three trophies/achievements associated with completing Stranger tasks: