There is an interview with Alexander Jacobs available in Film Quaterly, Vol. 21, No. 2 (Winter 1968 – Winter 1969), pp. 2-14
How did the script for Point Blank come to be written?
There were three main versions of the script. The first I did during my first stay in Hollywood, in four weeks, and that consisted of writing the script once and then rewriting it completely. I only had four weeks because I was working on a picture in England. John gave me the script that the Newhouses had written, which was a craftsmanlike piece of work but very old-fashioned. And the idea was to make a thriller that was enterprising. What I argued from the beginning was we couldn’t make an Asphalt Jungle, we couldn’t make a Harper, we couldn’t make a Sweet Smell of Success. I thought all those days were over-television had scraped them clean.
We had to do something completely fresh. We wanted to make a film that was a half reel ahead of the audience, that was the whole idea. We made a vow that we’d have no people getting in and out of cars, no shots of car doors opening and closing, unless there was a really important reason. And then I wrote a second version which consisted mainly of long letters from me in England to John in Hollywood, plus long telephone conversations on casting and all sorts of things, and of course letters from John, which were amalgamated into a second-draft script.
And then I went out to San Francisco on the shooting of the picture the first two weeks. The ending and the beginning of the film take place in San Francisco and that’s where we shot. I then wrote a lot more stuff including a completely new ending and a new beginning, some of which was done in script form, some of which was in discussion, and some of which was literally dictated to a girl and rushed out to location as they were shooting. This included the whole idea of using the sightseeing boat as a means of linking the past and the present. I wrote a new ending which wasn’t used. I don’t really agree with the ending in the film at the moment — I think it’s evasive — but that’s the one that was finally shot.