D.P.O.
At its core, episode three of season three is a stalker case, with local teen Darin Peter Oswald (Giovanni Ribisi) harbouring a dangerous obsession with high school teacher Sharon Kiveat (Karen Lorre). However, their town of Connerville, Oklahoma, manufactures lightning, and Oswald was once struck, leaving him with the ability to manipulate electricity.
The curiosity of agents Mulder and Scully is aroused by the death of a local teenager outside an arcade in the town. His death is the fifth such electrocution in a short time period, and during the course of their investigations, they discover that Oswald is the only person in town to have been struck by lightning and survive. When they find his initials on a game inside the arcade, along with a time stamp that places him at the scene of the crime, he becomes the prime suspect. They just need to figure out how he did it.
As the investigation zeroes in on the suspect, his obsession with his teacher begins to spiral out of control – leading him to remotely attack her husband, inducing a heart attack. This action leads Mulder and Scully directly to Sharon Kiveat at the local hospital, and they place her under their protection as Oswald approaches. A confrontation causes Oswald’s rage to escalate – attacking the local sheriff (Ernie Lively) with electricity – to the point where Oswald is repeatedly struck by lightning, and finally rendered unconscious.
At the conclusion of the case, we find that Oswald has joined the ranks of violent, extraordinary perpetrators consigned to nameless, anonymous locked rooms for further scientific study.