End of the Line Main Story, The Institute Quest
This quest will be triggered or can be aquired when you complete Powering Up quest.
Related points of interest
Stages of "End of the Line" quest
1. Speak with Father
After meeting with the Directorate, I need to talk to Shaun about what comes next.
Father wants you to eliminate the leaders of The Railroad.
2. Kill Desdemona
The leaders of the Railroad need to be eliminated, to make sure they can no longer interfere with Institute operations.
You can talk to Desdemona before making a final decision.
3. Eliminate the Railroad leaders
If you killed Desdemona then you have to kill all the people in Railroad HQ.
4. Speak with Father
There is one more threat, you have to eliminate for The Institute - Brotherhood of Steel.
5. Quest completed
Next / new quest is Airship Down (Main Story, The Institute).