"I’m not sure Doctor Who has ever faced a higher level of difficulty than it did with 'Rosa,'" says Caroline Siede of Sunday's powerful and emotional episode that left viewers in tears. "I was incredibly nervous heading into this episode because there were so many ways it could fail. It could fall back on the sanitized myth that Rosa Parks was just an old woman who was too tired to give up her seat. It could inject wacky alien hijinks into a politically charged moment of history. Or, worst of all, it could rob Rosa of her real-life agency by presenting the Doctor as some kind of inspirational influence on her actions. But writers Malorie Blackman and Chris Chibnall are incredibly smart about how they structure the episode. 'Rosa' isn’t about the Doctor and her companions changing history, it’s about them guarding the timeline so that Rosa’s heroism itself can change the world."