Walkthrough for American Imperialism of Red Dead Redemption: Undead Nightmare.
*. You need to complete Birth of the Conservation Movement, Paternal Pride, Dinner for Two, and Missing Souls missions first to start this mission.
1. After doing the four needed Survivor Missions, go to W mark in the map to meet Dickens at the Solomon's Folly.
2. Go to the Campsite in the Brown Dot at The Scratching Post.
3. Kill the zombies around the house to get reward you need from survivors.
4. Follow Blue Dot and go to Yellow Dot to get the uniform you need.
5. Go to Brown Dot in the Train Station at the Benedict Point.
6. Clear the station from any zombies.
7. Zombies will attack you but since the train is moving too fast, there is nothing worry about.
8. Protect soldiers from group of incoming zombies.
9. Go back to train's engine room and release the brakes to move the train.