David Tennant could have a Doctor Who season 9 return all lined up.

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The man behind the Tenth Doctor was seen visiting set last week, according to Spoiler TV, and the actor's presence in Cardiff could signal an upcoming meeting between Ten and Twelve (Peter Capaldi).

Doctor Who is planning on revealing the reason behind Capaldi's existence in Pompeii and Torchwood, and considering Ten's previous dealings with the man named Caecilius, there is now a firestorm of speculation regarding Tennant's potential return.

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"With regards to my Roman alter-ego, there will be a... he may appear again," Capaldi during an edition of Apple's Meet the Filmmaker (via Doctor Who TV) "He will certainly be invoked."

It is unknown how Who will solve the problem of multiple Capaldis, but Moffat will utilize former showrunner Russell T. Davies' solution. Davies' was also seen on set recently.

"When I cast Peter and Russell got in touch to say how pleased he was, I said, 'Okay, what was your theory and does it still work?' and he said, 'Yes it does. Here it is...'" Moffat told Nerd3.

Find out more when Doctor Who returns to the BBC and BBC America on Sept. 19.