A Loose End

A Loose End is a Brotherhood of Steel side quest in Fallout 4.

Quick walkthrough
Captain Kells wants the Sole Survivor to kill Virgil. Alternatively Kells can be convinced with a Charisma check that Virgil has been cured and is no longer a threat.

Detailed walkthrough
The quest begins when the Sole Survivor speaks with Lancer Captain Kells. He informs them that the super mutant 'Virgil' must be killed. The Sole Survivor then must find and talk to Virgil. They will then have the choice to either kill Virgil or spare him and lie to Captain Kells. After picking either option the Sole Survivor must report back to Captain Kells who will reward them with the Visionary's T-60c helmet.