End of the Line

End of the Line is a quest in Fallout 4.

Quick walkthrough
The quest is started automatically upon the completion of Powering Up.
 * 1) Speak with Father
 * 2) Kill Desdemona
 * 3) Eliminate the Railroad leaders

Detailed walkthrough
Father will ask what you think of the Directorate's intention to destroy the Brotherhood of Steel. Even if you say it is a mistake to do so, Father will insist that it is the only right decision because otherwise the Institute will be destroyed. He then informs you that your involvement with the Railroad is known and asks if you are ready to turn on The Railroad. Even if you say that they are your allies and argue to save them he wants you to destory them. If you refuse, he will say 'it is an order'.

After killing the leaders of the Railraod return to Father. He tells about a plan to drive the Brotherhood of Steel out from the Commonwealth. To discourage them from returning this plan is about teaching the Brotherhood that the Institute at any time and place can turn their own technology against them. You are instructed to the speak with Dr Li about this. The quest completes and the next starts.

Bugs

 * Quest won't progress on the (Eliminate the railroad leaders) stage even though all of them are killed. A fix is by completing the stage using the console: