Niezawodny plan

Sidney Sheldon is known for complex plots, but I wonder what sparked the idea for the story's major surprises. Did he plan the twists from the start or let them evolve?

The romance added an emotional layer, but sometimes it felt like it overshadowed the suspense. Was that intentional, or just my reading experience?

Each character seems to have their own agenda, which creates a web of deception. Did any character's choices surprise others, or did they feel inevitable?