Suspected Synth

Suspected Synth is a quest in Fallout 4.

Quick walkthrough
When returning to the settlement after establishing the location for the Minutemen, one will come come upon a settler brandishing a weapon at another individual. The first settler is accusing the other of being a synth. It is up to the player character to decide of what to do with the person accused.

Detailed walkthrough
Walking in from the wasteland, you can hear yelling and other signs commotion coming from the outpost. There in the middle of the compound, a settler is aiming a pipe pistol at another settler saying that she has been watching this one for some time and is ready to kill the synth.

The accused settler says that she is not a synth. So, it is up to you to decide on whether or not to kill the settler.

In talking to the accused, you will have a "Interrogate" option [ orange speech check ], kill the settler, let her go, or let the person accusing to decide.

Upon successful interrogation, the accused might or might not admit to being a synth. Also, if she confesses to be a synth, the let her go option changes to where you have to lie and say that they are not a synth. If she is not a synth, the let her go option remains instead. If she is not a synth and she is allowed to be killed either by the player or the accuser, a few of the other settlers will claim "Oh! I guess she wasn't a synth afterall." There is a bug where, even after the conflict has been resolved, if you kill the accused settler, they settlers repeat, "I guess she wasn't a synth afterall" but becomes hostile nevertheless. Same can happen if the player attacks the settler along with the accuser.

So, it is up to you on whether to let the synth live or die. By choosing either the "kill her/him" option or "your call" options, the accused synth dies. Otherwise with a "let her/him go" or the lie, the synth will live.

With this quest, it does not provide information yet of whether the synth is hostile or not.

Bugs
It's possible to walk into the settlement to find the objective suspect dead, this seems to make to quest impossible to accomplish as the quest marker will hover above the dead suspect.