The Doctor

In 1807 the population of a Chinese coastal village take cover in their houses as the lone figure of a female pirate walks into their town square intent on smashing a stone statue of a Sea Devil victoriously holding a small human figure. An old man, called Ying Wai, confronts the female pirate who is digging into the statue with her sword, trying to make out some inscriptions. Ying Wai tries to warn her off, knowing that she will unleash something inconceivable, by holding her at sword-point. But he is to late as their squabbling is interrupted when glowing green cracks start to spread across the statue. The entire stone statue then explodes - falling away to reveal a living Sea Devil, dressed like the statue and holding a glowing cutlass. The Sea Devil promptly kills Ying Wai.

Meanwhile, on a nearby beach, the TARDIS materialises and The Doctor and her traveling companion, Yasmin Khan, exit decked out in period clothing, and are immediately upset to realise their efforts misfired because they have somehow ended up four hundred years off from their intended date. Further banter follows from fellow travelling companion, Dan Lewis, when he exits the TARDIS dressed as a pantomime Western pirate, complete with an eyepatch and a hook. Hearing screams coming from the nearby village, they rush there to find the Sea Devil wreaking havoc upon the village, massacring its inhabitants. They draw the Sea Devil away from killing Ying Wai’s son, Ying Ki, and the female pirate (who had been thrown to the ground by the exploding statue). However, the Sea Devil thwarts The Doctor’s attempt to catch him in a fish-net, before summoning a flying ship, which he uses to sail off into the distance. Aboard his ship, the Sea Devil addresses his crew, who answered his call, coming out of hibernation. He has them summon the Hua-Shen, a huge sea creature at their command, who attacks a lone human fisherman in his boat, as it returns to the surface.

Back in the village a baffled Doctor is left to analyse Ying Wai's dead body enabling her to confirm to Ying Ki that the female pirate did not kill his father. The woman in question introduces herself as Madam Ching, whom an enthusiastic Doctor recognises as a notorious pirate queen. Madam Ching further explains that she is seeking the lost treasure of the Flor de la Mar, which was supposedly found in the 16th century by the ‘great captain’ Sin Ji-Hun only for his ship to have sunk nearby.

Pirate Dan

Intrigued by this and why the Sea Devils are present The Doctor and Yasmin return to the TARDIS so that they can locate the Sea Devil’s ship but the TARDIS systems fail to trace it as it has been cloaked, leading The Doctor to suggest they talk with Madam Ching again. But to do so they need to acquire the lost treasure of the Flor de la Mar themselves, so as to use it as a bargaining chip to get Madame Ching on their side. To find it, she makes a short hop in the TARDIS so that they can see for themselves what happened to Ji-Hun, and thus discover the exact location of the shipwreck on the seabed.

Back in the village, and still thinking that Madame Ching killed his father, Ying Ki and Dan sneak aboard Madame Ching’s ship. Dan however, notices that Madame Ching has no crew. Madame Ching, who captures Dan and Ying Ki, reveals she is after the treasure because she needs it to pay the ransom for her kidnapped crew, which includes her two young sons. Madame Ching’s ship is then attacked by the huge sea creature that was unleashed by the Sea Devils.

Yasmin and Dan

In 1533, the TARDIS materialises on Ji-Hun's ship. There The Doctor and Yasmin witness a strange scene as Ji-Hun forces all his crew (including his second-in-command Lei Bao) to jump overboard or be killed. The Chief Sea Devil teleports in and Ji-Hun kneels to him, stating that he has fulfilled his request and his ship is ready for the Sea Devil's use. The Sea Devil however, betrays Ji-Hun making it clear that he does not intend to hold up his end of the bargain, considering that he is not bound by promises made to a mere ‘land-crawler’. The two lock swords as the ship begins to sink, prompting The Doctor and Yasmin to hurry back to the safety of the TARDIS.

The Doctor sets the co-ordinates to take them back to 1807 and to the location of the shipwreck, now that they know the exact location where the Flor de la Mar went down. The TARDIS materialises underwater, with an oxygen bubble allowing The Doctor and Yasmin to walk on the ocean floor to investigate the shipwreck. After admiring the underwater scenery, they soon realise that even though they are at the right location, there is no trace of a shipwreck. Suddenly, the seabed drops beneath their feet, revealing itself to actually have been the back of the Hua-Shen. Just after The Doctor and Yasmin re-enter the TARDIS the sea creature catches it in its jaws and carries it away.

The TARDIS is taken to the Sea Devils’ undersea lair where The Doctor and Yasmin emerge to be confronted by the Chief Sea Devil. The Doctor and Yasmin are shown the Flor de la Mar, which has now been retrofitted with alien technology. The Doctor realises that this is the very ghost ship that the Sea Devil flying earlier. The Chief Sea Devil reveals that they are seeking a particular piece of the lost treasure of the Flor de la Mar - known as the Keystone. Pretending she has the Keystone, The Doctor, with Yasmin, use it as leverage to see the ship. Aboard the ship, they are shown Ji-Hun, who has been kept alive in stasis in a living death for hundreds of years as punishment for tricking the Sea Devils. The Doctor manages to talk with Ji-Hun, who reveals that he was never in league with the Sea Devils but merely to trick the Chief Sea Devil into thinking so in order to buy his crew time to escape with their lives, and to safeguard the Keystone which he had given to his most trusted crew member, Lei Bao, back in 1533, just before the Sea Devils arrived. The Keystone, he explains, is a gem of extraordinary power and must not be obtained by the Sea Devils as they will then use it to execute their plan to flood the earth which will then enable them to repopulate the Earth. The Chief Sea Devil though returns and calls The Doctor’s bluff saying the sea creature has discovered the Keystone. Before the Sea Devil can kill The Doctor, Yasmin in desperation manages to use the necessary controls to abruptly make the ship return to the surface, freeing Ji-Hun in the confusion.

A Sea Devil

The Sea Devils’ ghost-ship rises up right next to Madam Ching’s ship, which was being attacked by the sea creature. Dan, Ying Ki and Madam Ching are surprised by the sudden appearance of the Sea Devils’ ghost-ship. They are even more surprised when The Doctor, Yasmin and Ji-Hun swing over on ropes. However, The Doctor barely has time to figure out that the Keystone is in fact being worn as a necklace by Ying Ki, who is the descendant of Lei Bao, before the Chief Sea Devils teleports aboard Madam Ching’s ship and takes it at sword-point before returning to his ship.

Intent on taking it back before the Chief Sea Devil can sink the ship again to take the Keystone to the Sea Devils undersea base and use it to trigger a mechanism that will flood the entire Earth, The Doctor and her friends swing back over to the ghost-ship where a sword-fight ensues. But they are too late as the Chief Sea Devil announces that the Keystone has already arrived in their undersea base, just before, to The Doctor's dismay, he is killed by a vengeful Ji-Hun. The Doctor takes control of the ship and sinks it again, instructing Dan to keep an eye on Ching and Ji-Hun and help them keep the Sea Devil crew at bay, while she and Yasmin make their way to the control centre of the underwater base to try and stop the mechanism.

The Doctor is able to tamper with the Sea Devil’s alien technology but to completely destroy it requires two cables to be held together. Initially, The Doctor volunteers to stay back, while the others escape, to sacrifice herself by holding the mechanism in place as it explodes, until Ji-Hun persuades her to let him lay down his own life instead, as he has no wish to return to a world that is no longer his own. This allows The Doctor and Yasmin to make it back to the TARDIS in the nick of time, with the treasure chest containing the treasure of the Flor de la Mar. Examining it, Madam Ching confirms it will be enough to save her crew. Apologising to Ying Ki for failing to save his father, she offers him a chance to start a new life as part of her crew, which he gleefully accepts.

The Doctor, Yasmin and Dan then say their goodbyes. Back on the beach Dan, sitting by the TARDIS, phones his friend Diane, timidly asking if they could meet up again at some point so that he'll have someone to talk to about his ‘mad adventures’. Meanwhile The Doctor and Yasmin are by the waters’ edge when she tells Yasmin that she wished that this would go on forever - knowing that her time as the Thirteenth Doctor will soon come to an end.