We’re counting down to another regeneration on Doctor Who, although exactly who will replace Jodie Whittaker to become the Fourteenth Doctor remains a tightly guarded secret. (No, it’s not Tom Holland.) But the BBC this weekend dropped a teaser for Legend of the Sea Devils, one of three special episodes airing this year to mark Whittaker’s final days as the Thirteenth Doctor.

As previously reported, the recently concluded 13th season was particularly impacted by the COVID-19 pandemic. (That’s the 13th season since the franchise restarted in 2005, not the 13th season since the show debuted the day after the Kennedy assassination). Instead of the usual 13 episodes, S13 only planned for eight because of the pandemic. Ultimately, showrunner Chris Chibnall decided to cut the season down to just six episodes, with a complete narrative arc rather than the episodic structure that has been more typical of the series. (The decision is not unprecedented, however. The Trial of a Time Lord in 1986 was also one complete narrative.)

Collectively, the six-episode arc was given the subtitle Flux. In it, the Doctor and her companions encountered a universe-ending anomaly intent on killing the Doctor. The crew also faced a smorgasbord of classic Whovian alien races: the Ood, the Cybermen, the Sontarans, and the Weeping Angels. While some critics found the narrative arc confusing—almost inevitable when the Weeping Angels are involved—and the finale disappointing, it was generally a solid season.

Conspicuously absent from Flux were the Daleks, but that’s because Chibnall was saving them for the first holiday special, Eve of the Daleks, which aired on New Year’s Day. The special introduced a new kind of Dalek, the Dalek Executioners, who sought revenge on the Doctor for her actions in the S13 finale. The Doctor and her companions Yaz and Dan were caught in a time loop, thanks to a TARDIS reset (necessary to repair the TARDIS from damage incurred from the Flux). Every time the loop reset, it would shorten by one minute and was destined to collapse entirely at midnight.

Legend of the Sea Devils, in comparison, is a classic Doctor Who period story. In it, our heroic Time Lord encounters a famous personage from the past—in this case, a notorious pirate queen in 19th-century China named Zheng Yi Sao, aka Madame Ching. Born in 1775, historians speculate that Madame Ching may have started out as a prostitute or madame on a floating brothel.

Her life changed forever in 1801 when she married the notorious pirate Zheng Yi, who hailed from a long family of pirates. Madame Ching proved to be a valuable asset, using her diplomatic skills to help her husband consolidate the various pirate fleets into a loose confederation. Each fleet had its own distinctive flag color (red, black, blue, white, yellow, and purple), and Zheng Yi took command of the largest Red Flag Fleet.

When Zheng Yi died in November 1807 at age 42—he fell overboard during a gale, which seems an ignominious end for a pirate—Madame Ching took over the entire confederation. She had the support of Zheng Yi’s nephew as well as his adopted son, Zhang Bao. (“Adopted” isn’t quite accurate; the boy was abducted from his family at 15 and forced into piracy. It seems to have been a common practice.) While Bao took over his father’s command of the Red Flag Fleet, he clearly wasn’t the boss. Historical records indicate that Bao obeyed his stepmother’s orders and “consulted her on all things before acting.” The two were also romantically involved.

Many battles and much pillaging followed, but the mounting opposition from the Qing Chinese government, the East India Company, and the Portuguese Empire—all of whom suffered significant losses to the pirate confederation—eventually became too powerful. This occurred as the pirate confederation was showing cracks in solidarity: the leader of the Black Flag Fleet, Guo Podai, openly fought Bao in late 1808 and surrendered to Chinese authorities shortly thereafter.