Stranger missions are optional missions in the Red Dead Redemption 2 story mode that usually involve very peculiar individuals who need help in completing a variety of tasks.

The American Inferno, Burnt Out is the final stranger mission available in the game. It becomes available during Epilogue 1, and so can only be started when John Marston becomes the playable character.
Quest Initiation
The American Inferno, Burnt Out is unlocked after completing the Home of the Gentry? mission in Epilogue 1, which is one of the late missions in the story chapter. To start the mission, you have to head toward a hill in West Elizabeth, to the south of Strawberry.
On the hill you will meet Evelyn Miller, who is the author that wrote many of the books that Dutch loved to read. After a short conversation, the writer will invite John to his cabin in Tanner's Ranch.
Part II
The second part of this stranger mission is available one full in-game day after the first one has been completed. You can either play the game normally or make camp and sleep for a while to make time pass.
Once a full day has passed, Evelyn Miller's cabin will be marked on the map. Head there and watch a cutscene where Evelyn Miller tells John he wants to show him something. Mount your horse and follow the man. On the way, you will find a trapped deer, which must be freed by pressing the X or A button repeatedly.
After freeing the deer, you will continue riding until you reach a hunters' camp. Evelyn Miller will provoke the hunters and a firefight will begin. Activate Dead Eye and shoot all of the hunters down before they get the chance to fire at you. Another cutscene will play and the second part of the mission will be complete.
Part III
The third part of the mission is available after a full in-game day has passed. You can either play the game normally or sleep at camp to make time pass.
Once a day has passed the marker will appear again on Miller's cabin, but you won't be able to have any contact with him, as he is working on another book and will not eat, drink or go out until his draft is finished. John can prevent him from dying from exhaustion by placing food in front of the cabin's door. Wait for some time to pass then come back to the cabin to see how he's doing.
Part IV
The fourth part of American Inferno, Burnt Out mission becomes available once a full in-game day has passed. Sleep at camp to make time pass.
This part of the mission is identical to the previous one. Miller is still writing and will not go out for any reason whatsoever. Leave some food in front of the door then come back later to see how he is doing.
Part V
The fifth and final part of this stranger mission is available after a full in-game day has passed.
After the marker appears again on the map, head to Evelyn Miller's cabin. He is nowhere to be found and you can only hear flies buzzing around. Enter the cabin and you will see that Miller has died. Pick up the letter nearby in which he states that he wishes to be burned. Then grab the watch from the desk and interact with the curtains to light the cabin, fulfilling the writer's final wish.
At this point, the mission will also be complete. If you have followed all of our Stranger mission guides, you will also have completed all the optional missions available in the Red Dead Redemption 2 story mode!