New Doctor Who companion Varada Sethu makes surprise early debut

Doctor Who always knows how to surprise viewers, and new episode Boom had a special one in store for fans because it marked the unexpected debut of Varada Sethu — the Doctor's future companion.

Varada Sethu was cast as a companion to the Doctor for season 2 earlier this year, with the actor first being seen filming with Ncuti Gatwa in January before the BBC officially confirmed she was joining the series. There was speculation that Sethu had replaced Millie Gibson in the sci-fi series, but this was confirmed not to be the case when the BBC revealed both actors will be companions in the next season.

Warning: This article contains spoilers for Boom

Who does Varada Sethu play in Doctor Who?

Sethu makes her debut in Boom, where she portrays an ordained Anglican marine named Mundy Flynn, who comes across the Doctor (Gatwa) and Ruby Sunday (Gibson) on the planet Kastarion 3 whilst running after a young girl named Splice. The meeting happens after the Doctor stands on a landmine and is unable to move, and Ruby is grappling to find a way to save him.

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Splice went to the Doctor's location looking for her father, and Mundy is ready to defend the little girl at all costs so is immediately on the offensive with the Doctor and Ruby.

Mundy reveals to them that her people are at war with the mysterious Kastarions, and that she is part of a religious community, who are fighting a seemingly endless war. They fight on the basis of faith in their leaders alone because they have never seen their enemy.

The Doctor tries to warn her that their battle is part of the agenda of the Vallenguard, who believe in making as much profit from war as possible. Or as the Doctor puts it, war "keeps you dying, keeps you buying" so the algorithm is pushing Mundy and her people to continue fighting.

In the end, Mundy comes to understand what the Doctor is telling her but it all seems to be too late as the timer on the landmind counts down. However, the Vallenguard is taken down by the AI remnants of Splice's dead father who helps hack into the system and tear it apart from the inside after the Doctor tells him to think of his child.

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With the day saved and the Doctor free from his impending doom, he and Ruby decide to head out on another adventure, but before they do so he promises Splice that he will return to their planet one day and even tells her to prepare his favourite food — fish fingers and custard. Though her father is dead, Splice is not alone because she has Mundy there to look after her.

The Doctor's declaration that he will come visit suggests that Mundy will cross his and Ruby's path again, however showrunner Russell T Davies has confirmed that Sethu's return will be "timey wimey" and that Mundy is not the character she will return as.

Sharing an image of the actor on Instagram, Davies wrote: "It’s a delight to welcome Varada to Doctor Who, earlier than expected, though things are about to get timey-wimpy. That’s the end of Mundy Flynn’s story, so quite how Varada returns will be revealed next year."

Sethu also shared in a statement: "I’m so excited the world has finally met Mundy Flynn, it was such a joy to take my first spin in the Whoniverse! I’m so grateful I get to come back for more, but you’ll all have wait and see how that manifests in the new companion role."

With that being said, it seems viewers will only learn how Sethu's companion comes into play in the 2024 Christmas special or in season 2. Until then, we can enjoy her performance as Mundy Flynn.

New episodes of Doctor Who premieres on BBC iPlayer at midnight every Saturday, and then airs at 6.50pm on BBC One.