Ep 10. The Girl Who Waited

The Doctor and his companions, Amy and Rory, find themselves on a planet called Apalapucia, a planet that's supposed to be a popular tourist destination. However, they quickly discover that something is wrong when they encounter a strange green fog. They soon learn that the planet is under quarantine because of a deadly virus called the Chen-7, and anyone who contracts it must be left behind on the planet to die.

As they navigate the planet, they hear a mysterious voice calling out for help. Following the voice, they find a room full of futuristic medical equipment and a video feed of Amy, who has been left behind for decades in a different part of the planet after being infected with the Chen-7 virus.

The Amy they find is not the same Amy they know - she's older, hardened, and has been through years of survival on her own. In the ensuing chaos, the Doctor and Rory come up with a plan to rescue her, but there's a catch: they can't save both versions of her at the same time. One Amy will have to be left behind, and the other will go with them.

As the two Amys face their uncertain fate, they each struggle with their own identity and sense of self. For older Amy, the prospect of meeting her younger self and missing out on so much is a difficult pill to swallow, while younger Amy feels trapped and mistrustful of her older self.

As the Doctor, Rory, and the two Amys race to escape the planet before the quarantine seals them in, they also face a moral dilemma: which version of Amy should they save? The Doctor, a time-traveler himself, understands more than most the consequences of interfering with time and changing the course of history. Meanwhile, Rory feels the weight of his love for Amy and doesn't want to leave her behind again.

As the episode comes to a close, the characters face a heart-wrenching decision about what to do. The Girl Who Waited is an emotional powerhouse of an episode that explores the complexities of identity, time, and love.