Jossen was a 22nd century Vulcan operative who turned rogue after engaging in shady dealings.

He was one of the seven rogue operatives whom the V'Shar had assigned T'Pol to capture. T'Pol was able to apprehend five of the operatives, but Jossen and another operative, Menos, managed to escape.

Several years later, T'Pol once again caught up with the operatives, this time tracking them to the planet Risa. Believing the operative was reaching for a weapon, T'Pol shot and killed Jossen. Menos, however, escaped once again.

Distraught over the fact that she had taken a life, T'Pol undertook the Fullara to suppress her memories of killing Jossen. These memories would resurface in 2152, when T'Pol apprehended the seventh and final operative, Menos. (ENT episode: "The Seventh").