Sinclair

 was a mercenary who was searching for the cure to the mysterious blue boils disease for his partner prior to October, 2287.

Background
Shortly after ditching the Gunners, Robert MacCready met Sinclair, a fellow contractor who was looking for the same thing: A cure for the mysterious blue boils for his partner. He found information that indicated Med-Tek Laboratories was experimenting with a universal cure at its Medford facility and MacCready joined his exploration party. Equipped with security codes to breach pre-War automated security, they only made it a short way in before feral ghouls pushed them back. They never made a second attempt, as Sinclair's friend died before they regrouped. Unwilling to go any further he gave the codes to MacCready, who clung to them. Seeking to succeed where he and Sinclair had failed to save his son Duncan from the same fate.

Appearances
is mentioned only in Fallout 4.