Green for Danger was a good title. The name set the stage for intrigue and skulduggery to come. And without that title, most would have left the movie quite early. They would have felt as though they were watching a very expensive, (due to the cost of the top notch cast). early version of a 1980's TV mid day soap opera set within a hospital.
But, just in the nick of time comes the building of the drama that is worthy of the title.
Once the law shows up, it moves marvelously and holds the viewer's, by now insatiable curiosity, to the end with many (guessing the murderer wrongly) episodes before the end.
And, just as an aside, I have a feeling that the author of the blockbuster book, COMA found his inspiration by seeing this movie or reading the book by Christianna Brand.