Jonas Grabowski was a human-Bajoran-Trill hybrid who served as an agent of the Temporal Cold War claiming to be from the 31st century. He presumably belonged to the same watch-dog organization charged with preventing or minimizing alterations to the time-line as Daniels, encountered repeatedly by the crew of the Enterprise (NX-01) in the 22nd century.
During the First Betreka Nebula counterstrike, Grabowski posed as the beta-shift flight controller aboard the USS Lambda Paz. He appeared to have been killed during the battle. He was memorialized as part of a service when the Lambda Paz was docked at Deep Space 9. (Star Trek: Lambda Paz: " Divided Loyalties", " The Tides of War, Part 1")
Grabowski later reappeared to Limis Vircona and Rebecca Sullivan when he helped the two officers escape Sindareen custody. He also made modifications to the weapons and shields of the runabout USS Potomac in the event that the ship should encounter any "Death Stars". Grabowski then asked that Limis keep these modifications on a need-to-know basis with her crew. That need to know took place when the Lambda Paz had a subsequent confrontation with the time-traveling ships.
Limis's next encounter with Grabowski was on Bajor in the 31st century. Limis had surrendered herself to Gul Enic Hadar after the Lambda Paz took heavy damage. Grabowski was instructed to transport her off, which created the alternate timeline he was hoping to avoid. (Star Trek: Lambda Paz: " The Tides of War, Part 1")