He is the 7th victim of Jason Voorhees.
A young man from the city, Jeff Dunsberry attended Paul Holt's counselor training center in Packanack Lodge near Crystal Lake. In 1984, Jeff and Sandra traveled to Crystal Lake in Jeff's pickup truck to go to Paul Holt's counselor training center in Packanack Lodge. Reaching the outskirts of the town, Jeff and Sandra stopped at a payphone to get directions from their friend Ted Bowen and, while distracted, failed to notice their truck getting towed by local gas station owner Max. Realizing his truck is being towed after Sandra pointed it out to him, Jeff hung up on Ted and began running after Max through the town streets, yelling for him to stop. Eventually, Max did stop and Ted appeared, welcoming Jeff and Sandra to God's country, and revealing the entire towing incident to have been a prank he cooked up to get the two there earlier.
With Ted in tow, Jeff drove off to the Packanack Lodge, briefly stopping to move an old tree that had been placed in the middle of the road near a sign for Camp Crystal Lake, realizing that the place was on the same lake they are. Eventually getting to the Packanack Lodge, Jeff and Sandra, after the orientation meeting with Paul, attended a campfire, where Paul told the story of Jason Voorhees and Camp Crystal Lake. After Paul finished his story, Jeff, along with everyone else present, was shocked when Ted jumped out of the bushes wearing a monster mask and brandishing a spear in another prank he had concocted with Paul. Paul then told everyone that Jason drowned, his mother got what she deserved, Camp Crystal Lake is off limits and to stay away from that site. 
The day after the campfire, Jeff, during a beach party with the other trainee counselors, was convinced by Sandra to go check out Camp Crystal Lake. Wandering through the woods, Jeff and Sandra reached the old campgrounds, where they found what appeared to be the mangled remains of fellow counselor Terry McCarthy's pet dog Muffin. Shortly after coming across the dead animal, Jeff and Sandra were found by local policeman Deputy Winslow, who took them to the Packanack Lodge. During a meeting between Paul and Winslow, Jeff and Sandra were sent on their way and afterward Paul told his assistant Ginny Field to make sure the duo get no seconds on dessert later.
Hours after trespassing on the old campgrounds, Jeff and Sandra, when Paul offered the chance to the counselors to go into town for one last night of fun, were barred from going due to the incident with Winslow earlier. Disappointed about being left behind, Jeff passed some time by arm wrestling Mark Jarvis in the main cabin, before being convinced to go upstairs by Sandra.
Making love with Sandra in their room, Jeff failed to hear Jason Voorhees enter the room. Before Sandra could warn him about Jason, Jeff was skewered by Jason with Ted's spear, which the killer drove through Jeff into Sandra and finally through the bed and into the floor. After killing Jeff, Jason took his body and hangs it from the ceiling with bed sheets behind the door of the room, where Vickie Perry later bumped into it moments before getting killed herself.
- His death is ranked as an honorable mention in WatchMojo.com's Top 10 Brutal Jason Voorhees Kills.
- In Friday the 13th: The Game has a loading screen showing Jeff and Sandra's death.
- Friday the 13th Part 2 (1981)
- Friday the 13th: The Final Chapter (1984) (flashback and mentioned)
- Friday the 13th Part VII: The New Blood (1988) (flashback;corpse)
- Friday the 13th Part 2 (1988)