THE RAILROAD 04 - Operation Ticonderoga
Triggered by talking to Desdemona any time between completing Story 11 - Institutionalized and starting The Railroad 05 - Precipice of War
Note: This quest can be bypassed (deliberately or by accident) if you fail to talk to Desdemona between completing Story 11 - Institutionalized and starting The Railroad 05 - Precipice of War. Once Precipice of War has begun, you can no longer start this quest. There is no penalty for this, but you will miss out on the XP and rewards for this pretty simple quest.
Objective: Go to Ticonderoga safehouse
After hearing about the coursers at the safehouse, you'll need to travel there (you may have already visited this location during an earlier Railroad quest). Wind your way through the streets until you reach the marked building and head inside the elevator. Descend into the depths of the structure and when the doors open, a courser by the name of X9-27 will intercept you.
Objective: Kill all coursers
You will have a couple of persuasion options here, but your main purpose during this quest is destroying both of the coursers in this building. Immediately after the conversation concludes, blast the courser in the face with your best weapons to bring it down before it can use stealth.
You'll then have to work your way down the building through multiple floors full of synths to find the second courser on the lowest level. Remember that synths have less resistance to energy weapons, making the fights easier if you use them. When you use the terminal to open a marked door, you'll encounter the second courser. This one will be ready for you so it will be harder to bring down. Use what cover you can and whittle down it's health until it expires.
Objective: Report back to Desdemona
Fast travel back to The Railroad headquarters and talk to Desdemona to finish up this short quest.