Mission Aboard The Mona LisaEdit
He was assigned to serve under Sergeant Zhao Heng Lopez when her squad, ordered by Commander Tobias Foucault, was sent to investigate the prisoner transport, the Mona Lisa, within the debris field of Installation 04, which was destroyed by John-117. Unknown to the Marines, the ship had been commissioned by the Office of Naval Intelligence, whose operative, John Smith, had been secretly researching the Flood on the Mona Lisa.
After a firefight with a group of unarmored Sangheili in the ship's cargo bay, the Marines received orders to purge the Mona Lisa's NAV databases in accordance with the Cole Protocol. They split up into two teams, with Lopez's team heading to the Mona Lisa's bridge, while Corpsman Benti's team set to destroy the backup database in the engine room. Gersten was assigned to Benti's team, along with Orlav, Tsardikos, and Clarence .
When passing through the ship's recycling plant, the team became under attack by a horde of Flood. Orlav was infected and managed to bite Gersten in the face. After the Marines got to safety in a maintenance room, Gersten began to show signs of Flood infection, and was shot in the head by Clarence without hesitation. His body subsequently reanimated, but Clarence shot him again, killing him permanently.