Complex sentence: To adapt "The Circular Staircase" for the stage, Rinehart and Hopwood made changes to the characters and plot; the most significant was the addition of the flamboyant villain whose nickname became the play's title.
Split into simpler sentences: To adapt "The Circular Staircase" for the stage, Rinehart and Hopwood made changes to the characters and plot. The most significant change was the addition of the flamboyant villain whose nickname became the play's title.