Doctor Who could be laying the groundwork for David Tennant's return as filming begins for the season 9 finale.

'Doctor Who' Season 9: Extra Long Hiatus Coming? Find Out Why Season 10 Could Be Delayed

The BBC series is in the midst of shooting the second half of Steven Moffat's two-part closer, and a new photo from set could reference the Tenth Doctor. Unseen since the 50 th Anniversary Special, Tennant's Time Lord could become the greatest surprise of the season.

"We sneaked a photo of Peter's script at last week's ep 12 read through," the Doctor Who official Twitter teased on Tuesday. "Now, where did we leave the pics of page 1..?"

The script's title is fairly blurry, but Doctor Who TV reports that the episode's name is comprised of just one letter - an 'X'. For those Roman numeral fanatics out there, this little hint could be the second sign that the Tenth Doctor is ready to bring his quick wit back to the BBC.

'Doctor Who' Season 9 Spoilers: Is Maisie Williams From Twelve's Past? Steven Moffat Teases The Truth

The first hint came last week when fans spotted Tennant and former Doctor Who showrunner Russell T. Davies in Cardiff, the home of the Doctor Who set. Both Peter Capaldi (Twelve) and Moffat have teased conclusion to Twelve's mysterious Pompeii appearance as Caecilius (Capaldi), a Tenth Doctor storyline that took place under Davies purview.

Could Ten be on hand to help set the record straight? Find out more when Doctor Who returns to the BBC and BBC America on Sept. 19.