Mitch is the manic owner of the Last Plank bar in Far Harbor. Mitch appears to be happy and optimistic when interacted with. Behind the bar counter, there is a letter, RUN!. Reading it states that Mitch believes the island is cursed, and wants everyone to get off the island.
If the Sole Survivor has the Awareness perk, and targets Mitch with V.A.T.S. it will show that Mitch has a naturally high energy resistance which is semi-common in Far Harbor.
When the Sole Survivor enters the bar Mitch will be trying to get everyone's attention. He will then announce the next round of drinks are on the house. When the Survivor first talks to Mitch they can ask him for something stronger than beer. If you pass the speech check he will give the Survivor a bottle of vodka which he says is top shelf stuff.