The series follows the events during the fall and winter of 1991–92, when John Ausonius shot a total of eleven people with an immigrant background. The series partly follows Ausonius during the execution of the crime, and partly the police's detective work. The series also provides an insight into Ausonius' earlier life, from high school age onwards.

1989年3月，瑞典南部的赫尔比10岁的海伦·尼尔森被谋杀。这个案子16年没有解决。《猎杀杀手》讲述了警察Per-Ake Akesson和Monica Olhed的坚定旅程，他们领导的调查小组最终不顾一切地找到了杀害海伦的凶手。