Were you looking for L. Jenkins from the Halo Graphic Novel, or for Captain Jenkins, who commanded during the Harvest Campaign?
Private First Class Wallace A. Jenkins was an infantryman in the UNSC Marine Corps. He was one of the first humans to engage Covenant forces during the First Battle of Harvest. In September 2552, Jenkins was stationed aboard the UNSC Pillar of Autumn during the Battle of Installation 04, eventually becoming partially infected by the Flood.
Early life and career
Wallace Jenkins was born on the Outer Colony world of Harvest. He was the eldest of three children of a farming family. In 2524, he joined the Harvest militia in an effort to make use of himself. His ambition was to join the UNSC Marine Corps as an officer. Though Staff Sergeant Avery Johnson frequently criticized him, he proved to be an extremely quick thinker and a competent militiaman. One notable event occurred when he and a fellow recruit, Forsell, were participating in a training exercise with all the other recruits in the Colonial Militia. The two were able to quickly assess the situation and go around the mock attack staged by Sergeants Johnson and Byrne. By doing so, they were almost able to win the exercise; however, a recruit named Osmo beat them to the goal. This earned Jenkins the trust of Staff Sergeant Johnson, and the two developed a close bond during the First Battle of Harvest.
Battle of Harvest
Jenkins was a superb sharpshooter and was assigned one of the few XBR55 Battle Rifles during the battle. Jenkins' entire family was killed when Gladsheim was attacked by the Covenant. He was deeply depressed after losing his family, and used his anger to fuel his hatred of the Covenant. The only person close to him to survive was his fellow sharpshooter and friend, Forsell. Forsell had saved Jenkins' life when the latter was blinded by rage, stopping him from trying to kill Tartarus. After escaping from Harvest, Staff Sergeant Johnson offered Jenkins, Forsell, and the remaining militiamen the chance to become Marines in his unit.
Fall of Reach
Jenkins was on board Reach Station Gamma during the Fall of Reach in August 30, 2552, still fighting alongside Staff Sergeant Johnson, as well as with Privates Bisenti and O'Brien. Their Friend-Or-Foe tags were detected by SPARTANs John-117 and Linda-058. The group was fighting a lance of Kig-yar rangers and defeated them with the help of the SPARTANs. The Master Chief also helped them destroy the navigation database of the UNSC Circumference, an Office of Naval Intelligence Prowler. After purging the Prowler's navigation database, the survivors escaped the station aboard a Pelican. They then boarded the Pillar of Autumn and traveled to Installation 04.
Battle of Installation 04
Upon arrival at Installation 04, the Pillar of Autumn was attacked by the Covenant. Jenkins escaped the ship in the same lifeboat as Sergeant Johnson and his squad. After meeting up with the Master Chief and fighting off Covenant patrols, they took Pelican Echo 419 to the newly established Marine Alpha Base.
Later, Jenkins, along with the rest of Fire Team Charlie, was taken on Pelican Victor 933 to what was believed to be a Covenant weapons cache. This believed weapons cache was actually one of Installation 04's Flood containment facilities. There, he, Captain Keyes, Sergeant Johnson, and Privates Bisenti, Mendoza, Kappus, and Riley were ambushed by the Flood. During the resulting fight, Jenkins panicked, and a Pod infector latched onto him. Johnson fired at the infector that was latched onto him but couldn't stop it from taking over Jenkins' body. Jenkins and the entire squad, save for Johnson, were turned into combat forms. However, Jenkins' Pod infector was weakened from centuries of containment, and could not fully control him. The infection process occurred normally, but unlike most victims of the Flood, who die instantly upon successful infection, Jenkins remained alive and terrified while the Flood took control of and mutated his body.  He was able to control himself to a small degree whenever the Pod infector was in pain, but when it had total command, he could only watch "his" actions. His Flood infected body attacked Johnson, throwing the sergeant out of the containment room, across a large observation chamber, and into a wall. Determined to escape, Johnson ran into a hallway and locked the infected Marines inside by using a spoofer.
The Master Chief would later watch the horrifying attack using the Recorder Chip from Jenkins' dropped Helmet Recorder. The video ended suddenly, right as the Pod infector hit Jenkins, and infected him.
Survival and death
The infected Jenkins followed a group of Flood to the surface, where they attacked a group of Orbital Drop Shock Troopers led by First Lieutenant Melissa McKay. Without complete control over his body, Jenkins, who was desperate to end his own life, attempted to get killed while assaulting the Lieutenant. The attempt failed, and he was captured by the ODSTs. Major Antonio Silva tried to interrogate him.
While being interrogated, the Pod infector inside Jenkins' body attempted to attack its interrogators by extending a tentacle through Jenkins' hand, snapping the bones and veins. As Jenkins described it, it was a "living hell". However, the parasite was knocked unconscious by the pain, this gave Jenkins the chance to reveal the imminent threat of the Flood beneath the base. He pointed with his other hand that had not been broken at the ground. Major Silva believed that Jenkins was pointing at his boot until Lieutenant McKay correctly interpreted that Jenkins was pointing down in fact and not actually at Silva's boot, and ordered a squad to exterminate them.
Jenkins was later taken to the Truth and Reconciliation while the Marines assaulted the ship. Jenkins knew that Silva planned to take the ship home to Earth. He also knew that there were more Flood present on the ship, and that they would inevitably escape and overwhelm the human population should Silva succeed in bringing the ship home. He thus overwhelmed the Pod infector inside him and tried to destroy the ship by destroying a fiber-optic pathway that linked the Control Room to the engines. He failed, but Lieutenant McKay, seeing the truth as well, destroyed the vessel for him by using a fragmentation grenade. The explosion severed the pathway, cutting off control to the engines and causing the ship to crash into the surface of Halo, where it exploded. The destruction of the Truth and Reconciliation mercifully ended his suffering.  Before he died, he managed to mouth the words "Thank you" to the Lieutenant.
List of appearances