Warning: Spoilers ahead for Doctor Who season 15, episode 3, "The Well."end of Doctor Who season 15, episode 1, "The Robot Revolution."

The TARDIS is unable to take Belinda home, so she is forced to become the traveling companion of Ncuti Gatwa's Fifteenth Doctor in season 15 as they take "the long way round." Her relationship with the Time Lord is frosty at first, but she quickly warms to him in Doctor Who season 15, episode 2, "Lux." By the time of "The Well," the two are comfortably interacting as though they've been friends for years, and Belinda discovers she's more like the Doctor than he had yet to realize.

The Doctor & Belinda Are Both The Last Of Their Kinds In Doctor Who Season 15

The Doctor is the last Time Lord, and Belinda is the last human

The final moments of "The Robot Revolution" reveal that the Earth has been destroyed. Thankfully, Belinda was away from her planet at the time of its destruction, so she didn't share the same fate. Therefore, after Alan's death in the season 15 opener, Sethu's character is the last remaining human in the entire universe - in the present-day, at least. After a trip to Miami in 1952, the Doctor and Belinda's trip 500,000 years into the future for "The Well" comes with the revelation that no one has ever even heard of humans because of Earth's destruction.

Missbelindachandrakind from "The Robot Revolution" and the squadron from Lombardo in "The Well" are not human, but they look it.

The Doctor, as he pretty much always has been, is also the last of his species. Not only is he the last of the Time Lords, but he's also the only known member of the species he was revealed to be during Chris Chibnall's divisive Timeless Child storyline. So, Belinda now has this trait in common with her new friend, which creates an interesting sort of dynamic between the Fifteenth Doctor and his companion.

Belinda Being The Last Human Should Bring Her & The Doctor Closer

The 2 friends now share a startingly similar Doctor Who backstory

The Doctor has long lacked someone who could truly understand the pain of being the last of their kind, and now he has that in Belinda. It's obviously not a desirable scenario, and he won't be happy that the Earth is gone, but now that both of them know the unique pain that comes from being so profoundly alone, they'll form a very deep bond. For Belinda to go from someone who never wanted to be in the TARDIS in the first place to someone who has nowhere else to go is one of Doctor Who's most heartbreaking companion arcs.