A Federation anthropologist at the hidden observation post on Mintaka III, fatally injured when the station's reactor fails and exposes the team to the people they are studying.
Dr Mary Warren is a member of the Federation anthropological team on Mintaka III and appears in the third-season episode Who Watches the Watchers, set in 2366.
With Dr Barron and Palmer she watches the proto-Vulcan Mintakans from a concealed post behind a holographic rock face. When the reactor powering the disguise fails, an explosion wrecks the station and all three are hurt. The Enterprise beams the casualties to sickbay, but Warren's injuries are too severe and Dr Crusher cannot save her.
Her death is the first cost of the accident. Its other consequence is that the Mintakan Liko sees the outpost and, after being healed aboard the ship, takes Picard for a god.