I thought he did a great job as a retiring detective. He was low key yet showed compassion with his dying wife. His anger was subtle but effective. This could have been one of his finest performances. Kind of like John Wayne in the Shootist.
It's undoubtedly one of his best performances, although the movie has a few issues with regards to the killer, Sinatra is superb here. Whilst I've always been of the opinion that the real story here is between Sinatra and Dunaway. Although her role isn't substantial, the relationship between her and Sinatra rings true and is very touching.
Gordon Jenkins' score is also terrific. It's almost a match for Bernard Herrmann's score for Taxi Driver, although it's quieter.
NOW TARZAN MAKE WAR!