He was on duty in 2370 when the Enterprise-D crew were infected by a virus later designated as Barclay's Protomorphosis Syndrome. He informed Commander William T. Riker about Starfleet's inquiry into the status of the new weapon systems test.
He was later killed by a devolved crewmember while seated at the helm console on the bridge. Upon analysis of his body, Data surmised Dern was undergoing the beginnings of the syndrome at the time of his death. (TNG: "Genesis")