In "Lucky Day," Ruby Sunday Is a 'Doctor Who' Companion On Her Own

Though Doctor Who ostensibly follows the adventures of a two-hearted alien who travels through space and time in a blue police box, the show's heart is most often found in the stories of the companions alongside him. Showrunner Russell T. Davies has always been interested in the idea that traveling with the Doctor is merely a means by which ordinary people discover that they are capable of extraordinary things. But the question of what happens after these adventures conclude and the companion returns home also fascinates him.

We've seen glimpses into the post-TARDIS life of previous Davies companions like Rose Tyler (Billie Piper) and Donna Noble (Catherine Tate). Episodes like "School Reunion" and "The Power of the Doctor" have touched on the disorienting nature of trying to go back to living an everyday life after experiencing something so profoundly amazing. But "Lucky Day" does something unprecedented, focusing entirely on companion Ruby Sunday's (Millie Gibson) life after leaving the TARDIS, giving her an Earth-bound adventure in which the Doctor barely appears, and expanding the scope of the series beyond the world of the Doctor and his blue box.

Ruby's life changed after traveling with him, but their time together also affected the person she became. Intriguingly, those changes are not always entirely positive ones. Ruby is stronger, more self-assured, and more capable than when we first met her in "The Church on Ruby Road," but she's also lonelier, less trusting, and more guarded. She's battling something that looks an awful lot like low-grade PTSD, and while she ultimately chooses to repay hurt and cruelty with kindness and mercy in the same way that the Doctor would, she still has a fair amount of healing to do of her own.