"Detach locomotive" is a mission objective in Sequence 2 / Memory 01: A Simple Plan
Walkthrough[edit]
Follow the on-screen prompt to use the whistle. This will draw in the nearby Thug and allow you to get a quick cover kill. Start heading forward after that. You can see another Thug a few cars up. Approach him stealthily. Follow the prompts on screen to dispatch this Thug with Throwing Knives. Jump to the next car.
There is another thug who will walk in front of you. Follow the prompt on screen to perform a quick throw with the throwing knife. It will not kill you target but they will be severely weakened here. You can follow it up with a second knife for the kill or just rush them and beat them down. Either way, be sure to loot the body to have a chance at getting a Throwing Knife back.
This is a chest in the next covered car. To get to it, climb onto car and then move to the left-hand side. You will see a prompt to enter the open window. Press it to get inside and have access to the chest. Now turn back toward the front of the train and continue forward. Climb onto the top of the next car. Run across it and then air assassinate the Thug who is on the next car. Follow that up by beating up the next thug. Continue forward for a few cars after that.
A number of cars up you will find another pair of Thugs to deal with. Close the distance and eliminate them. Cross the next covered car and drop down onto the open car after that.
Ahead of you is another covered car. Inside it is a sleepy Thug and a chest. Sneak inside it, eliminate the Thug and open the chest for more money and Throwing Knives. Hop out the window and continue the trek forward to the engine car. Get to the coupling between the engine and the rest of the train. Hit the prompted button to get Evie to detach the rest of the train.
