Trivia

First English language film of French director Claude Chabrol. Though filmed in Canada which hosts both French and English as native languages, French director Claude Chabrol chose to shoot the film in English rather than French as he felt the story would work better on film in the native language of its novel.

Debut theatrical feature film of Canadian actress Lisa Langlois

Claude Chabrol thought that New York, home of Ed McBain's "87th Precinct", was too unwieldy, so big that it would obscure his intimate explorations of character and swallow the movie, so Chabrol instead relocated Ed McBain's "87th Precinct" to Montreal, Canada which spoke his native tongue of French but still had a North American setting. Despite being set in Canada rather than the USA where Evan Hunter's source novel was set, the movie still retained the "87th Precinct" for the picture.

While the original French version of the film is composed by Claude Chabrol's regular composer Pierre Jansen, for the English release a new score was composed by Howard Blake. Blake said: "In March 1978 I had just finished arranging and recording period dance music and acting as Musical Director on the film El misterio de Agatha Christie (1979) and was waiting for 2 weeks for the final cut to be ready for scoring. I was down at Shepperton and happened to meet Peter Collinson, famous for directing Faena a la italiana (1969). He asked if I would have time to write 'a few cues' for a film by Claude Chabrol called Hermanos de sangre (1978). I said I thought that Chabrol always had his own composer to score for him, but Peter explained that he and Michael Klinger had acquired the English-language film rights outright and they thought with a new score the film might succeed in the USA/UK market. I had some qualms about this and whether I had the time, but was talked into it and wrote a score within the 2 weeks, recording it at CTS Wembley on April 5th with Sid Sax's 'National Philharmonic Orchestra' and my favourite engineer John Richards. I used a very dark scoring for the horrifying opening with 4 bass flutes, Bass Clarinet, 2 bassoons, Contra-bassoon, 4 Horns, 3 trombones, harp, celesta, 2 percussion and 2 double basses. Later when Donald Sutherland meets the apparently-innocent young girl out at her parents in the country I introduced a string orchestra. The composed music added up to about 20 minutes in all. I have no idea whether Claude Chabrol ever heard it. If he did I hope he wasn't too upset since I was a great fan of his films from Le beau Serge (1958) and Les cousins (1959) onwards."

Actress Stéphane Audran and director Claude Chabrol were married. They had been married for for twenty-two years around the time that the film was released in America .