Doctor Ehrehin i'Ramnau tr'Avrak was a Romulan engineer working towards the building of avaihh lli vastam (warp seven stardrive) for the Romulan military. He was there when they were testing a prototype ship, which exploded and caused damage to the ground installation. He watched his lab assistant Cunaehr die in the accident and was beamed out by a waiting Romulan warship.
He was sent to recover on an isolated estate on the then-Romulan world of Nelvana III to recover when he was kidnapped by a Romulan terrorist group the Ejhoi Ormiin in order to create a warp-seven stardrive so they can overthrow the Romulan Senate. The plan was foiled when Section 31 agents, former Enterprise chief engineer, Commander Charles Tucker III and Tinh Hoc Phuong, were sent in to sabotage the development project. They had been deceived about the true nature of the Ejhoi Ormiin and Phuong was murdered by their leader, Sopek. Tucker however managed to escape with Ehrehin and he attempted to escape with him to space claimed by the Coalition of Planets.
Ehrehin, deduced correctly that Tucker wasn't a Romulan, but still helped him fix their ship and get a message to Captain Jonathan Archer when he told them about the Romulan's plan to attack Coridan III and destroy it.
After the genocidal attack on Coridan III, Ehrehin swore never to help the military finish the avaihh lli vastam, but stll refused to defect, being a patriotic citizen of the Romulan Star Empire. So he stunned Tucker so he could escape to Admiral Valdore's fleet. However, he set the computers on their scoutship to resume returning to Coalition space at high warp. He recorded a message to Commander Tucker wishing him luck on his future endeavors to sabotage the Romulan war machine. Once back in Valdore's custody he resumed the senile old man routine he used while in the hands of the Ejhoi Ormiin. (ENT novel: The Good That Men Do)
He died in 2155 on Day 30, Month of K'ri'Brax when the Ejhoi Ormiin raided his office. (ENT novel: Kobayashi Maru)