The final institute main quest. This is quite simple, albeit a bit touching, of a quest.
1. Make your way to the Institute, and navigate to Father, who is in his deathbed
2. Speak to him and offer your son some final parting words
3. Shawn passes away, and the ending cutscene for the game begins
Notes:
Once this quest is completed, Father's memorial will appear in the Institute in front of the Robotics division, and Institute synths will patrol the Commonwealth's military checkpoints.
If the player kills Father before his natural death, the player will become enemies with the Institute, and this quest will still complete.