S5·E17 The Invisible Killer

Pilot Dan Crowley is grounded by his doctor for his intense behavior. A delusional man who's constantly trying to prove himself, he believes the doctor's daughter should be his, even though she is happily engaged to his boss. When the couple and the doctor go for a hunting trip in the woods, Dan follows and, at night, begins firing on their cabin using a rifle with an infrared scope.