Shaun (synth)

Shaun, also known as S9-23, is a prototype synth created by the real Shaun, and lives in the Institute, unless the Sole Survivor opts to destroy the Institute and arrives during the mission The Nuclear Option, after which he sends him to the Commonwealth or leaves him to die.

Background
Shaun was created at the behest of Father, the director of the Institute, and is a Gen 3 synth based on the real Shaun's DNA.

Madison Li expressed discomfort and irritation according to her personal holotapes as Advanced Systems has been tasked with the creation of Shaun. She was unable to understand the scientific need for the creation of a child synth, something that Father did not bother to divulge. In actual fact, Shaun was created not for any research or scientific advancement, but simply on the whim of Father.

When the Sole Survivor arrives to the Institute to locate their child during Institutionalized, they are briefly led to believe that the synth Shaun is the real one in order to test the child's responses. Shaun responds negatively and calls for help from Father before being deactivated. Father then acknowledges that "it is still a prototype".

Other interactions
If the player completes one of The Nuclear Option quests, and synth Shaun is not left behind in the Institute, he will ask the player character to bring items (e.g. a hot plate) so he can 'take it apart' and in return will build useful items for the player character, such as weapon mods and the Wazer Wifle. Additionally, the player character can ask Shaun to live with them, and can send him to a number of locations, similar to a companion, although he is not able to be assigned to beds, like many other NPCs. He cannot be commanded to move throughout the settlement. He will stay within the confines of a small area. (e.g. near the Minutemen Radio Operator in the Castle.)

If the player instead completes the Nuclear Family quest, Shaun will be interactable and found within the Advanced Systems Lab. The player has the ability to choose where Shaun will live by talking to him. If you subsequently decide to move him to another settlement, it must be done via the workshop interface. Shaun will sometimes ask for all sorts of parts in order to build something.

Effect of player's actions
After The Nuclear Option, if Shaun is not left behind in the Institute, upon meeting with the player character again and being interacted with, he will give them a holodisk named Shaun's holotape as instructed by Father, saying "I didn't listen to it, so I dunno what it says, but I think it's important." The holotape, recorded by Father, reveals that he re-programmed Shaun to believe that he was the son of the player character, and pleads with the player character, saying "I would ask only that you give him a chance. A chance to be a part of whatever future awaits the Commonwealth."

However, if the player chooses the Nuclear Family option, they can still obtain the holodisk, but Father's speech will differ, still revealing that he reprogrammed Shaun and saying "Both he and you deserved a chance to... To be a family. Please, take care of him."

Should the Sole Survivor leave Shaun in the Institute following the sabotage of the reactor, he will go down with the facility-although if the Survivor sides with the Railroad and chooses to abandon Shaun, Tinker Tom will say he will still teleport Shaun out of the Institute and have the child taken care of (as the Railroad's main objective is to free all synths). Whatever the case, Shaun never appears in the game again.

Appearances
Shaun appears only in Fallout 4.

Bugs

 * The player character may be unable to give Shaun the first junk item he asks for after speaking to him following the Institute ending. When attempting to interact with him after retrieving the item, he will speak, but there will be no options to give it to him.
 * The player character may be unable to adopt Shaun if they choose the Nuclear Family ending. In addition if they are able to adopt him, they may not be able to move him to another location.
 * It seems synth Shaun's speech is bugged, as he may address male characters as mom, as well as female characters as dad.
 * Attempting to send Shaun to another settlement via the building menu can result in him shutting down as if someone had uttered his reset code. He will then remain standing there indefinitely, but during conversation his lips will still move. The only way to fix it is reloading an older save.
 * The player character may be unable to talk to Shaun while exiting the Institute during the Brotherhood storyline. This will effectively cause the player to be stuck in the Institute with no way out.