Swedish director Bo Widerberg filmed this police thriller from a novel, 'The Abominable Man', following his film for children, Stubby An earlier film version of a Sjoewall-Wahloo novel, 'The Laughing Policeman', was made in Hollywood by Stuart Rosenberg, for The Man on the Roof, the authors of the book collaborated with Widerberg in preparing the script

The film opens on a hospital at night A former police chief, much hated by his past colleagues, is being treated in a private room A man slips in and kills him The case is assigned to Superintendent Beck of Homicide, who gradually discovers that numerous people had filed formal complaints against the victim, alleging different instances of abuse It also becomes apparent that the murderer could well be a policeman.

The Superintendent isolates one suspect and goes to call on his parents as the man himself cannot be reached During his visit, a patrolling policeman in central Stockholm is killed by a sniper The patrolman's partner, rushing to his help, is also shot As the carnage grows, Beck learns of unexpected and odd connections between the suspect and the police chief He is then faced with the problem of cornering the marksman who is continuing to shoot at police from his roof-top sanctuary Beck cordons off the area and sends in police by helicopter, but an accident causes him to change his plans.