It's a gamble that certainly pays off. Often David films have a sense of anti-climax. After his early heroics, even becoming king seems to lack dramatic pay off. But then A Story of David doesn't have that either. Instead it limits its narrative to the story of David having to flee from Saul and surviving his forces in the wild until he and Saul are reconciled when David spares his life. Certainly this is the only film amongst the David biopics that manages to uncover the inherent tension in this part of the story.
There are a number of interesting innovations here. Doeg the Edomite relatively minor role in the scriptures is greatly inflated to one as Saul's key advisor, poisoning his mind. Indeed Doeg comes to hold far greater prominence than Abner, who whilst he is steadfastly loyal to Saul nevertheless looks on with disapproval at many of his actions. There's also an enhanced role for Abiathar. As per 1 Sam 22 & 23 he escapes the slaughter of the priests at Nob and flees to be with David. Though still a boy he becomes one of David's inner circle - certainly not implausible given his later position as (joint?) High Priest. But he also becomes the one from David's mighty men who draws water from the well only to see David pour it out to the Lord (1 Chron 11). (This is the only David film to include this incident as far as I recall).
The film also gives a significant amount of screen time to Abigail and her first husband Nabal, who is played by a relatively restrained performance by Donald Pleasence. This was three years before his role in The Great Escape brought him acclaim from outside the UK.
By this stage, though, the plot is beginning to peter out. The final scene where David and Joab sneak past Doeg into Saul's tent lacks both the necessary tension and a sufficiently strong resolution leaving the film without a satisfactory ending.