18th of July, 1384

Alexandria, The Mamluk Sultanate, Earth

The TARDIS materialised on the port of Alexandria. The Doctor, Jessica, and Khaldun all left it, going into the decently-busy area. "Here's the plan." the Doctor began while taking out what looked like a keyring from her satchel, "I cannot stop Khaldun's family from boarding the ship, so I am bringing this keyring with me. When the time comes, I will press the button, materialising the TARDIS around me and anyone immediately surrounding me. Unfortunately for you, Jessica, you can't join me and Khaldun."

"Why not?" Jessica asked.

"Because the locals aren't going to be fond of you and you don't have any psychic paper on you. You will still have the important role of making sure that the TARDIS is stable when materialising around me. You've communicated with it before. I'm confident you can do so again."

"On it, Doctor." Jessica got back into the TARDIS.

"Khaldun, let's get your family home."

"Then we shall start." Khaldun replied in determination.

The Doctor smiled. "Fasaeidan!" Both the Doctor and Khaldun were looking around, searching for the ship that Khaldun's wife and sons were going to board before finding one heading for Constantinople. "Excuse me, guard." the Doctor said, "May we board that vessel?"

"Not unless you pay." the guard replied.

"I need to go to Constantinople." The Doctor showed the guard her psychic paper. "Me and Ibn Khaldun here have been requested to teach in that city by none other than the Roman Emperor himself. So, may we board?"

"I'm sorry, Doctor Mayer."

The guard got out of the way of the Doctor and Khaldun, letting them on board. "So that is the hard part out of the way." Khaldun said.

"No, that's the easy part. The hard part is finding what is going to cause the ship to begin sinking. We find that, we find a way to save your-"

"Abdurahman?" a female voice interrupted the duo.

Khaldun recognised the voice immediately: it was his wife's voice. "Farah!" he said before running to her.

"Abdurahman, I thought that you were busy teaching people."

"I was, but then the Sultan said that the Roman Emperor requested for my teachings and that of my colleague."

"And he is..."

"A she, actually." The Doctor brought out her psychic paper again. "Doctor Sybil Mayer, I teach in the field of physics."

"Your voice has a weird tone."

"I'm English. I moved to Alexandria a few years ago and as a Woman of God, I have paid my taxes for being Christian instead of Muslim."

Farah did not fully believe the Doctor. "And you're going to Constantinople with my husband for educational purposes."

"I can assure you that I do not intend to put any stress on your marriage." The Doctor showed off her wedding ring. "I'm married and loyal."

"Good. Abdurahman, follow me. Sybil..."

"Please, call me Doctor."

"Doctor, stay away. I still do not trust you much."

"Alright, I'll leave you be." The Khalduns left the Doctor behind, giving her free room to investigate. The ship was in the middle of its route when the Doctor looked over the port side of the ship. It was then that she noticed something: there were some wave ripples forming in the sea, all of them beginning to head towards the ship. They were ripples that she recognised as something darker. "Khaldun!" she said as she began to run towards the Khalduns.

On the other side of the ship, Khaldun was talking to his wife. "I forgot the reason why you are on this trip." he said.

"I simply wish to know what all the fuss is about Constantinople." Farah replied, "A short and simple vacation, no more than a couple of days."

"Unfortunately, I'll be there for more than a couple days. Tutoring is a busy job."

"Who are you tutoring, father?" one of Khaldun's sons said.

"Well, Abdul, I am to tutor the emperor's son. I am preparing him to become his success-"

"Sorry to interrupt." the Doctor said hurriedly, "I have to be here."

"I told you to stay away, Doctor."

"What I'm about to say is urgent. Really urgent. You're all in danger."

"Are you trying to kill me and my husband?"

"No, Farah. She's right. You are in danger."

"Abdurahman, what are you on about?"

"Missus Khaldun, this isn't your husband that's currently in Cairo teaching. He's from nearly a year in the future..."

"...a future where you and our sons are gone."

Farah was beginning to get scared. "Are you a demon?"

"No. I'm the woman who is trying to save your life." The Doctor got out her keyring. "This brings my mode of transport here, enveloping you so that you can all escape. You don't have to fully trust me, but you shouldn't bury your head in the sand either."

"Give me a reason to join you, then."

"There are wave ripples alongside this ship. It's a sign that the Sea Devils are upon us."

"And they are...?"

"Inhabitants of Earth since time immemorial, know technologically advanced than any human. If it weren't for me, they would be the rulers of this planet by now. They also look like humanoid turtles."

Farah smacked the keyring out of the Doctor's hand. "Now I know you are insane. Humanoid turtles who are way more technologically advanced than us? There's no way such a species exi-"

One by one, some humanoid turtle-looking figures jumped into the ship, proving Farah wrong. The Doctor knew for sure that this was the cause of the sinking of the ship. Each of the humanoids wielded a scimitar, and their armour resembled those donned by the Mamluks themselves, with the exception of a helmet resembling the head of a turtle. The Sea Devils were here.