Summer has finally arrived and Sonoko arranged to go to the beach with Ran and their friend Masumi. Of course, Conan and Kogoro came with them, and they didn't mind it at all (Especially Kogoro, who could watch beautiful ladies in swimsuits, much to Ran's displeasure)

"Oh, look at that sea!" Masumi said, excited.

"Come on, Conan, let's take a swim!" Ran said, holding the "child"'s hand.

Conan nodded.

The girls and Conan headed towards the sea and had some fun together, or rather, the girls. Conan spent all the time in the sea trying to mind his own business and hiding his flustered face from Ran.

"Ah, that was fun, wasn't it?" Masumi said.

"Yeah, thanks for inviting us, Sonoko," Ran said.

"Oh, no need to thank me! We're friends, after all!" Sonoko said. "Wanna get an ice cream?"

"Yeah!" the others said in unison.

Meanwhile, the TARDIS materialised not too far from the hotel

"Are you sure you don't want to come, Shiho?" the Doctor said, wearing a rainbow Hawaiian t-shirt and green board trunks with a couple of red question marks on it.

"No, thank you," Shiho said, yawning. "Too tired from swimming. Have fun."

"Alright then." the Doctor left the TARDIS.

Shiho returned to her room and noticed something odd: A futuristic-looking fob watch.

"Huh." She thought. "Didn't remember having that…"

The Doctor reached the beach and smirked. "Very well, let's begin." He pulled out his sonic screwdriver and activated its radar.

Meanwhile, Conan, Ran, Sonoko and Masumi were enjoying their ice creams.

While chatting, Ran noticed something interesting: The Doctor walking on the beach, wandering with the sonic screwdriver like a madman.

"Hey…" She said, pointing at the Doctor. "Isn't that John?"

"Who, the brat in the green suit?" Sonoko said.

"Yeah, it's him!" Masumi said. "Heeeey, John! Over here!"

The Doctor noticed the group and smiled as he approached them. "Oh, hi there! I didn't expect you to be here!"

"We could say the same." Ran smiled. "What are you doing here?"

"Oh, well, just…Wanted to take a swim, that's all. My parents are at the hotel, I'm old enough to hang alone." the Doctor grinned.

"Can I talk to you in private, Doctor?" Conan whispered.

The Doctor nodded and the two went to a more private place.

"Is there something wrong with this beach? Should I get worried?" Conan asked.

"Well, I don't know for sure. I'm investigating." the Doctor said.

"On what, exactly?"

"According to the recent reports from the JMSDF, several ships, both military and civil, sank under mysterious circumstances near this beach." the Doctor explained.

"Do you have any idea who might be the culprit?" Conan asked.

"I have, but I don't want to make any accusation until I have some proof." the Doctor said. "Just…Have fun with the others, okay? No need to worry."

"...Alright, but if you need a hand, you know where to find me," Conan said as he left. The Doctor did the same. However, not too far from there, hiding behind a wall, there was Masumi, who eavesdropped the entire conversation.

"Ships sinking, huh? Sounds interesting." She thought as she left too.

"Sorry for the wait." the Doctor said, as he and the boy with glasses returned to Ran and Sonoko.

"Took you long enough, you two," Sonoko said.

"Oh, there you are too, Masumi," Ran said. "Where have you been?"

"Sorry y'all, I went to the bathroom." Masumi chuckled.

"She also went away the same moment we did. Did she follow us?" the Doctor thought.

"Anyway, can we go back to the hotel? I'm a bit tired." Conan asked.

"Yeah, let's get back, I'm tired too," Ran said.

"You can go to the hotel if you want, I'll reach you later. See ya!" the Doctor left.

"I wanna go for another swim before going, I'll reach you later too." Masumi left.

Ran and Sonoko didn't mind it, but Conan glared at the tomboy detective, suspicious of her.

The Doctor kept investigating with his sonic screwdriver near the shore, far away from the beach, with Masumi stalking him. "Huh?" The Doctor noticed some odd footprints on the sand. "What a weird footprint…This doesn't belong to a human, for sure. Looks like it belongs to an amphibian…" He noticed burn marks near some rocks. "These marks certainly aren't natural, they must be the work of a weapon."

Meanwhile, at the hotel.

"Hey, where's your classmate, that tomboy detective?" Kogoro asked.

"You mean Masumi?" Sonoko said. "Well, it's been an hour since she went for a swim…"

"I hope she's okay…I didn't see John coming to the hotel, either." Ran said.

"I wonder if the Doctor found something." Conan thought.

Ran stood up and went to the hotel entrance.

"Hey! Where are you going?" Kogoro asked.

"I'm going looking for them," Ran said.

"Wait for me, I'm coming with you," Conan said.

The two went to the beach looking for Masumi and the Doctor.

"Seeing the beach so empty gives me chills…" Ran commented.

"Me too…" Conan said. "Over there! Footprints!" He pointed at the big and small footprints.

"Small and larger footprints…Maybe Masumi and John went there?" Ran said.

The two followed the footprints until they found something horrifying.

An enormous, thin turtle-like brown humanoid creature, wearing a kimono-esque outfit.

"What is that thing?!" Ran said.

"I don't know, RUN!" Conan and Ran tried to escape the creature, who tried to kill them by shooting the two with a side-arm weapon. Unfortunately, they quickly got surrounded by more of these creatures.

"What should we do?" Conan asked.

"I'll try to distract them, you go to the hotel and ask for help," Ran said.

"But-"

Ran started attacking a couple of these creatures, granting an exit to the boy. "Now's your chance! Go!"

Reluctantly, Conan obliged.

Ran tried keeping the creatures with her karate moves as much as she could until she managed to run away. But then, another creature dragged her away into the sea and vanished into thin air, leaving the other monsters confused.

Meanwhile, the Doctor was heading back to the TARDIS when he saw Conan running towards him.

"Doctor! Doctor!" He said.

"Conan, what's wrong?" the Doctor asked, worried.

"Monsters…Some monsters kidnapped Ran!" Conan explained.

"Did these monsters look like reptiles, like a turtle, for example?" the Doctor asked.

"Yes…Do you know them?" Conan asked.

"Unfortunately, I do. Remember when we went to Victorian London and met that Silurian, Va'astra?" The Time Lord asked.

"Yes, what about it?"

"You see, the monsters that kidnapped Ran, and who probably sank those ships, are a type of Silurians who evolved to live underwater, or as UNIT calls them…The Sea Devils ."

Ran regained consciousness. Her vision became clear and saw that she ended up in a cavern. She turned around and saw a Sea Devil.

The girl screamed in terror and jumped away from the creature.

"Have no fear." The Sea Devil spoke with a raspy voice. "I have no intention to harm you."

"Who…Who are you? Where am I?!" Ran tried to calm down.

"I managed to save you in time from the others, as for me, I am what you apes call 'Sea Devil'." The creature said.

"Sea…Devil…?" Ran repeated. "'Others'? What did they want from me?"

"We were once the original rulers of this planet, but Mankind stole that place from us. Thus, the desire to reconquer the Earth became stronger within us."

"Then…Why did you save me?" Ran asked.

"Despite I would like to walk over the Earth free, I do not wish for the extinction of Mankind." The Sea Devil explained. "But my comrades do, and I must stop them to avoid futile bloodshed."

Ran looked worried and confused about the explanation the Sea Devil gave her. "Is there…Is there something I can do?"

"I'm afraid not. Do not worry, you will be safe here." The Sea Devil put his hand on her shoulder.

"...Thank you." Ran smiled.

"I must go now, I will return." the Sea Devil said. "Say, what is your name, human?"

"Huh, Ran, my name is Ran." Ran introduced herself.

"Very well. I will return, Ran." The Sea Devil left the cavern.

Meanwhile, the Doctor and Conan headed to the TARDIS.

"So, what's the plan?" Conan said.

"Elementary, my dear Conan: We chase the Sea Devils-Hold on." the Doctor looked around.

"What is it?" The boy asked.

"You can come out, you know? I know you're there…Masumi." The Time Lord said.

Masumi came out from her hiding. "Fine, you got me…"

"How long have you stalking us?" the Doctor raised an eyebrow.

"Since you talked in private with Conan," Masumi said. "But it doesn't matter now, does it? Ran's in danger, I wanna help ya."

"Thank God I didn't say anything about my identity…" Conan sighed in relief.

"Yes, you're right. Come along." the Doctor said, as he entered the TARDIS.

"W-Where? In that Police Box?" Masumi commented, confused.

"Yes, just come in, will you?" the Doctor said.

"Okay, even if I don't understand how-WHAT THE HELL?!"

Like everyone who stepped inside that small police box for the first time, Masumi was completely shocked by the TARDIS' interior.

"It's…It's…"

"It's Bigger on the Inside, yes, yes, I know." the Doctor snarkily commented, as he pulled down the lever and the TARDIS dematerialised.

"Looks like we have company." Shiho went to the console room.

"Indeed. Masumi, this is Shiho, a 'roommate' of some sort. Shiho, this is Masumi Sera, one of Ran's classmates." the Doctor quickly said.

The two bowed.

The Doctor went away and quickly returned with several oxygen tanks.

"There you go." He said, "These should be enough for the journey."

"Okay, but, how can we find Ran in the ocean?" Conan asked.

"The same way we found Ayumi, by locating her vitals," Shiho said.

"Bingo!" the Doctor said. "I already set Ran's vitals on my sonic screwdriver. Let's-a-go!"

The group put on the diving equipment and went outside. Shiho remained in the TARDIS, in case things went south.

The trio followed the signal and arrived in the cavern.

"Guys!" Ran went to hug Masumi and Conan. "I'm so happy to see you!"

"Are you okay? Did they hurt you?" Conan asked.

"I'm fine, don't worry. Someone saved me in time." Ran said.

"And who saved you?" the Doctor asked.

"It was me." The Sea Devil reappeared, scaring the living Daylights out of the Doctor, Masumi and Conan.

"What is that thing?!" Masumi said.

"It's a Sea Devil! Everyone, behind me!" the Doctor ordered, pointing his sonic screwdriver. "Don't move! State your motivation at once!"

"Wait!" Ran said. "He doesn't want to hurt us! He saved me!"

"Who? That thing?" Masumi said.

"Rude!" the Doctor commented.

"It is fine, I suppose she has never seen someone like that before, I am not surprised that she is frightened.

"...So." the Doctor calmed down. "What do you want?"

"To stop my people from causing a futile massacre." The Sea Devil said with a determined tone.

"Be more specific, what do your people want to do to Mankind?" the Doctor asked.

"To destroy the humans and retake the planet via a powerful weapon." The Sea Devil explained. "A weapon powerful enough to drive into madness Mankind, making them return to their primitive state."

"How can we stop it?" Conan asked.

The Sea Devil showed them an odd-looking disc.

"What's that?" Ran asked.

"It's a bomb." the Doctor said. "You want us to blow up your people, correct?"

"I'm afraid it is the only way." The Sea Devil said with a saddened tone. "But I'll do what I must."

The Doctor smirked, impressed by the Sea Devil's resolution. "Very well, We'll help you. Any objections?"

The three humans shook their heads.

"Thank you." The Sea Devil said.

"You're welcome." the Time Lord said. "So, where are your people's base?"

"Our colony is not too far from here. We should have enough time to escape before the bomb blows up." The creature explained.

"I see." the Doctor said. "What about you?"

"I shall die with them." The Sea Devil calmly explained.

Good, so, I'll blow up the ship, you guys go back to the hotel."

"But-"

"Nah, let him do it, Ran. He can do this." Masumi said.

"Alright then, I'll go now. Lead the way, chap." the Doctor and the Sea Devil left the cavern, while the three humans returned to the surface.

The Doctor eventually arrived deep into the sea, where a ruined submarine rested.

"We have almost arrived. Do as I say now." The Sea Devil said.

The two entered the base and the Doctor pretended to be a prisoner.

"Let me go! Let me go, you big frog meanie!" the Time Lord acted.

"The traitor has returned." a Sea Devil guard spoke.

"I have come to redeem myself. I have brought this young ape as a prisoner, as a sign of goodwill." The Sea Devil said.

The two guards looked at each other and decided to let the two pass.

The Doctor was however thrown into one of the prison cells.

He wasn't alone over there, there were some corpses of men belonging to the Navy.

"Oh dear, they're not used to cleaning the cells, huh?" the Doctor thought. "Okay, let's get out of here."

He noticed an air vent, opened it with his sonic screwdriver and went inside.

He began exploring the vents, looking for a place to activate the bomb. After a while, he finally found it: The generator room.

He went in without making a sound and put the bomb on the generators.

"So, when I press this button, the timer will activate. I'll have a minute to get out of here before the detonation." the Doctor thought. "What a pity, if I had an adult body, perhaps I might have persuaded them to not wage war against Mankind. I doubt they would listen to a child. Oh well, here goes nothing, so long, pal."

The Doctor pressed the button returned to the vent and looked for a possible exit. He managed to find the room with several cannons for missiles. He went inside one of them and escaped from the base, which exploded instantly.

Conan, Masumi and Ran returned to the beach, hoping that the Doctor would return.

"Look! Over there!" Ran pointed to the Doctor emerging from the water.

"Mission complete, guys!" the Doctor waved at them.

Ran and Masumi hugged the little Time Lord, relieved to see him safe and sound.

"Everything's all right? You blew up the ship?" Masumi asked.

"I did, even though I feel bad for them." the Doctor said. "Anyway, can I ask you a favour? About all of this stuff…Let's not talk about it to anyone, okay?"

"I agree, I doubt anyone would believe us," Conan said, glancing at the Doctor.

"Yeah…Don't wanna spend the rest of my life in a Psych Ward." Masumi chuckled. "Alright, I'll keep my mouth shut."

"Same." Ran nodded.

"Alrighty, I'll go now. See ya!" the Doctor left the group.

Later, the Doctor was heading towards the TARDIS.

"Doctor, wait!" Conan arrived.

"Oh, what is it, Conan?" the Doctor asked.

"About Masumi…" Conan said, "Can we trust her?"
"I think we can. She's a nice girl." the Doctor said. "Besides, I still want to know why her surname is so familiar to me."

"Well, you time travel, maybe you met an ancestor of hers, or her parents when young? Oh, speaking of which…" Conan pulled out his flip phone and showed the Doctor a photo depicting Masumi and a preteen girl with blond curly hair and green eyes, who had a striking resemblance to the tomboy detective.

The child-looking Time Lord turned pale. "Where…Where did you find it?"

"Masumi had it in her wallet when she offered us ice cream. I took a photo of it. Do you recognise that blonde girl?"

"Yes…I think I do. You see, back in the 70s, I partnered with a woman for a couple missions for UNIT and the MI6's Joint Training. I think that woman must be Masumi's mother and the girl in the photo! Her name is…Mary Sera."

-To Be Continued-