Vehn is the Resistance member responsible for the capture of the Moshae as he helped the kett's Archon with the capture. He betrayed the Resistance because he thinks that the angaran are losing the war against the kett and because Evfra de Tershaav, leader of the Resistance, still risks the lives of Resistance members to protect the Moshae that he considers as a useless old woman. As the Archon was only interested in the Moshae, Vehn thought that he would stop the war if the Moshae was captured.
After his treacherous act, he runs to Kadara to hide from his fellow companions. Evfra kept his betrayal secret from everyone, fearing it would undermine faith in the Resistance. Eventually, the traitor Vehn is captured and put in jail by Sloane Kelly. As the angaran people in Kadara don't like what he did to the Moshae, Sloane Kelly decided to execute him.
During the hunt for the Archon, Pathfinder Ryder is sent by Evfra, to bring Vehn back to the Resistance and interrogate him about Archon's ship location. Vehn never saw the ship and doesn't know where it is, as he received his orders via a kett transponder. He suggests then that Ryder use the transponder he buried outside town to triangulate the Archon's position. Depending on how Ryder's previous conversation with Sloane went, Vehn will either be left in prison, or Ryder will help him out of jail and to meet the Resistance contact, Reyes Vidal.
If Vehn is set free by Ryder, he is sent back to Aya to be interrogated and killed by Evfra. However, the Moshae eventually convinces Evfra to let him live and make him work as a "volunteer" for servitude on the planet.