From Halopedia, the Halo wiki
Mission aboard Mona Lisa
Simmons was part of the Marine detachment under the leadership of Sergeant Zhao Heng Lopez, sent to investigate the prisoner transport Mona Lisa in Installation 04's debris field over Threshold. Without the knowledge of the Marines, the orders for the mission had come from the Office of Naval Intelligence whose operative John Smith had been secretly researching the Flood on the ship.
Qualified as a pilot, Simmons served as the copilot of the Pelican dropship piloted by Burgundy during the flight to the Mona Lisa. After entering a cargo bay aboard the Mona Lisa, a group of several unarmored Sangheili engaged the Marines. After the Marines had successfully defeated the attackers, Lopez ordered Simmons, along with Cranker, Maller and Sydney, to guard the Pelican and clean up the bodies on the bay's floor while the others went to find Rabbit, who had gone missing during the fighting.
Soon after, Simmons and the accompanying Marines became under attack by Pod infectors, and disappeared. Simmons would later become a Flood form, and was part of the horde of Flood that attacked the last surviving Marines near the ship's escape pods moments before the Mona Lisa was destroyed. After pushing herself and Clarence into the Flood mob, Corpsman Ngoc Benti saw the Flood form that used to be Simmons clutching a struggling Clarence.
Along with a number of other Marines, Simmons is not present the motion comic adaptation of The Mona Lisa.
List of appearances