Does Richard Widmark's brash physical energy in this movie remind anyone else of Klaus Kinski? Anyway, I watched the British cut with the 'happy' ending, which:
[…] doesn’t exist in the American version. Once the Strangler tosses Fabian’s corpse into the Thames, Kristo flicks a cigarette toward his body: The End. It’s among the bleakest endings ever conceived for a film noir or otherwise in this era.
— Brian Eggert (Deep Focus Review)
Regardless of whether it's one of the bleakest noirs, it's certainly one of my favourites.