Atonement: what is one main theme?

Most of the action in Atonement is seen through physical windows, which allow viewers to see but not necessarily hear or understand. Briony oversees Cecilia and Robbie at the fountain and is confused when their actions do not fit her preconceived, romantic idea of what ought to be going on. From a window Lola sees Briony stalking off to the island, not realizing her cousin dislikes her enough to behead her in effigy. Reading Robbie's unintended note and reflecting on the fountain scene, Briony is ready to misread the scene of passion she comes upon in the library as an assault on her sister and Briony prepares to indict Robbie. Although it is too dark to make out faces and though Briony has seen physical evidence on the true attacker, Briony makes what she "knows" become what she has seen and Robbie is wrongly sent to jail. When Briony later understands what she has done and determines to atone for it, it is a matter of too little, too late and she must turn to her fiction writing to tell the full, unvarnished story. Still, as a novelist, Briony comprehends that readers will want a happy ending and she fabricates a modest rapprochement. Looking out a window on the driveway where Robbie was arrested, as she had decades earlier, Briony comprehends that an author holds her characters' fates in her hands, but nothing can be done for her own peace of mind.