While fans knew that Peter Capaldi’s time on “Doctor Who” was limited, they also became concerned about his companion Bill. Pearl Mackie’s character was rumored to die in the Season 10 finale, but the end of her storyline turned out to be the beginning of a new life rather than death — at least that’s how showrunner Steven Moffat feels.

“I don’t think she is dead. She doesn’t die,” Moffat told “Doctor Who: The Fan Show – The Aftershow.”

While that’s true, it definitely seemed like Bill’s time on “Doctor Who” was coming to an end (though Mackie has not confirmed if she is actually leaving). Heather (Stephanie Hyam), who was introduced in the season premiere, has the ability to travel freely through time and space, and when Bill cried, Heather made Bill like her. It rescued Bill from life as a Cyberman, and Bill and Heather left the TARDIS to explore the world together.

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“So, she doesn’t die. She nearly dies and becomes something else,” Moffat noted. “I don’t know the future plans. I’ve kept away from them. I’ve put it such that — Heather does say, ‘Look, I can put you back on Earth if you want to go back and make chips.’ So she could. I kind of think in my head, she flies around the universe with Heather, that’s what she does.”

Doctor Who Bill Bill (Pearl Mackie) left the TARDIS to travel with Heather (Stephanie Hyam) in the “Doctor Who” Season 10 finale. Photo: BBC Worldwide

Bill nearly had a tragic ending after becoming one of the Mondasian Cybermen. Her mind was still in tact, but her body wasn’t. The people on the spaceship all feared her, and living as one of the Cybermen certainly didn’t seem like a great option. Becoming whatever species Heather has become and running off with her love interest seems like the best outcome for Bill.

Despite leaving the TARDIS, Moffat sees it as a happy ending for Bill because she gets to be with the woman she loves. “I don’t think ‘Doctor Who’ is that kind of show. ‘Doctor Who’ is a big-hearted, optimistic show that believes in kindness and love and that wisdom will triumph in the end,” the writer said. “I don’t believe it’s the kind of show that says there are bitter, twisted, nasty endings because it’s not.”

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To be fair, other companions in recent memory have had some fairly depressing endings. Rose (Billie Piper) was trapped in a parallel universe. Donna (Catherine Tate) was forced to forget the Doctor. Amy (Karen Gillan) was sent back in time by a Weeping Angel. As far as companion’s endings go, Bill is one of the happier ones.

Doctor Who Bill (Pearl Mackie) left the Doctor (Peter Capaldi) behind in the “Doctor Who” Season 10 finale. Photo: BBC Worldwide

Moffat will step down as showrunner after Season 12 and hand over the reins to Chris Chibnall. It seems the writer wanted one of his final outings to reflect the optimism of “Who.”

“It’s not gritty, it’s aspirational. It says, ‘It can work. And wisdom and kindness will triumph. And love will always come through in the end,’” Moffat explained. “I think there aren’t enough people or enough shows saying that and I’m damned if ‘Doctor Who’ is going to join in with the general chorus of despair.”

In any case, it seems like the Doctor will be on his own in the Christmas special. After Bill left the TARDIS, the Doctor woke up and tried to delay his regeneration. He ended up in a snowy village face-to-face with the First Doctor (David Bradley).

The “Doctor Who” Christmas special airs Dec. 25 on BBC America.