Just Imagine...

MerIanto

The object resembled a very large blue pearl, with tiny rainbows sparkling in it like oil spilled in a puddle. It was just sitting there on the pink sands of Pearl Beach, glimmering away in the sunlight.
"So... what is it?" Owen asked, peering at it and tipping his head to the side.
"I bet it's a Sea Dragon egg!" Sam exclaimed, getting down on all fours to inspect the object more closely, "if it hatches, I'm keeping it!"
"You say that like anyone else would want to keep it," Owen pointed out, "you're like an obsessive renther hen when it comes to baby alien animals."
"You can talk," Sam scoffed, "the minute one of us gets a paper cut you act like we're gonna hemorrhage!"
"Okay, you two," Ianto cut in, "I don't want this to end in tears so let's just take this thing and get out of here."
He bent over to pick up the strange object, but as soon as his fingers touched it, a jolt of pain coursed through his body. Ianto jumped back with a yelp, falling backwards onto the sand.
"Ianto!" Sam exclaimed, at his side in an instant, her long golden and red hair draping down onto his face.
"I'm okay," Ianto wheezed as Sam and Owen helped him sit up, "what was that?"
"I'll know when I take a look at you." Owen said sternly.
"Bawk bawk bawk..." Sam muttered close to Ianto's ear, and Ianto couldn't help but giggle uncontrollably.
"Oi," Owen said, "I'm not fussing, this is serious. We have no idea what that thing just did to Ianto."
"Yeah yeah yeah," Sam responded, rolling her green eyes, "we gotta find another way to get it back to the hub. What if I wrap it in something?"
"Be careful." Owen cautioned, slowly helping Ianto to his feet.
"Pfft. I'm always careful." Sam chuckled.
"There's mountains of evidence that disprove that statement." Ianto murmured, but Sam ignored him, taking off her shirt to reveal her dark tan shoulders spangled with freckles underneath. There was a set of pinkish scars on her right shoulder blade to match the one on her left eyebrow, and a blue spider tattoo below her left collar bone, partially covered by the strap of the crop top she was wearing beneath her shirt.
Sam bent over and wrapped the shirt around the object like a scarf, careful not to touch it directly. Owen and Ianto watched tensely.
"If this goes South," Sam murmured, "tell Jack, Hanna, Alexa, Lukie, and the triplets that their Ren died as she lived; saving a trainload of people."
"Oh c'mon, that's not funny!" Ianto exclaimed, and Sam shot him a cheeky grin. She gently lifted the makeshift sling off the sand, and the object didn't fall out.
"It's surprisingly light," Sam murmured, seeming perplexed, "doesn't feel any heavier than a pool ball."
"Well let's get it back to the hub so Tosh can look at it." Ianto said.
"Are you okay to walk?" Owen asked.
"I'm fine." Ianto assured him, ignoring the funny feeling in his legs. It was probably just the shock of whatever that thing had done to him.
However, on the drive back to the hub, Ianto felt increasingly uncomfortable. His skin was crawling and his legs were twitchy and sore. It was getting harder and harder to deny that something was wrong with him.
Once back at the hub, Ianto announced that he was going home because he didn't feel well. Owen was adamant about coming with him and Ianto reluctantly agreed. It would be better to have someone there than have Jack come home from picking up the kids to find him in a comatose state.
Owen drove him to his and Jack's house, and Ianto realized he was swaying on his feet as Owen helped him up to his bedroom. Ianto sat down on the bed and was about to lay down when his eyes drifted to the bathtub in the adjoining bathroom.
"Run me a bath." Ianto said.
"What?" Owen demanded.
"I need a bath," Ianto murmured, "I don't know why, I just need to be in the water, right now!"

Jack returned to find Owen's car in the driveway instead of Ianto's. That concerned him, but he didn't let it show in front of Gabby and Danny.
"UNCLE OWEN!" Both kids squealed when they saw Owen on the couch in the living room, having helped himself to the kids' goldfish crackers and trashy reality tv.
"Owen, what is going on?" Jack asked urgently as the kids leaped on top of Owen, covering his face in kisses, "where's Ianto?"
"He's upstairs having a bath." Owen replied casually.
"A bath? Ianto hates baths! Is this a prank?"
"I wish it was, Jack. I really do."
Jack could tell by Owen's face that he was sincere and felt the worry he'd been trying to push down bubbling back up.
"What's wrong with him?" He asked.
"Relax! You say it like he's sick!" Owen laughed, pulling Gabby and Danny closer to him.
"Well why did you leave him alone up there?" Jack demanded.
"Couldn't stand the smell."
"What smell?"
"Go up and see. He's not alone, by the way. Tosh and your renther are with him. Gwen wanted to stay so she could see your reaction but she promised to have dinner with Rhys tonight so she had to go home."
Jack frowned at Owen suspiciously, but didn't ask any more questions. He turned and walked up the stairs, hearing the sounds of water running and quiet splashing as he got closer to his and Ianto's bedroom.
"Ianto?" He called.
"In here, Jack." Ianto's voice sighed disgruntledly from the adjoining bathroom, along with faint laughter that sounded like Sam and Tosh.
Jack walked over to the bathroom and stopped in the doorway, feeling his jaw go slack.
Tosh and Sam were kneeling beside the bathtub, Sam grinning at him and Tosh covering her mouth with her hand to hide her giggles. The bathtub was full to the brim with water, and inside was a very grumpy looking Ianto Jones, with pointed blue ears and a long, scaly, blue and purple tail in place of his legs that had flopped out of the tub and spilled some water onto the floor.
"Is that really you?" Jack asked when he finally remembered how to speak.
"Who else would it be?" Ianto snapped, "and stop looking at me with that stupid face!"
"What happened to you? How did this happen to you?? AND WHY DOES IT SMELL LIKE FISH IN HERE???"
"Mermaid technology." Tosh spoke up.
"And mermaid pheromones," Sam added, waving a hand in front of her nose and sticking her tongue out, "just be glad we locked Hermes in Gabby's room, the smell was driving him nutso!"
"Hermes?" Jack echoed, before registering the frantic meowing of his and Ianto's cat from down the hall.
"Yeah, you might wanna check on him." Sam suggested.
"ABSOLUTELY NOT!" Ianto cut in, "if he gets out he'll run in here and start licking me again!"
"Well no wonder!" Sam laughed, "you smell like forty pounds of tuna!" 
Ianto flicked his tail and splashed water on her as Tosh burst out laughing. Sam squeaked and covered her face with her arms.
"We should be figuring out how to change me back!" Ianto said angrily. 
"I dunno," Jack said with a grin, "I kinda like the idea of having a sexy little mermaid all to myself."
"And on that note I'm going to go tell Owen to pick up Samuel and Akio from daycare." Tosh murmured, standing up and walking out of the bathroom.
"I learned about this technology while I was travelling with the Doc," Sam mused, "when humans and mermaids were together on earth, thousands of years ago when the Saint Lucia Relief Point opened for the first time, before it got damaged and the Rift closed. The mermaids - also known as the Qik - wanted to show humankind what their home planet was like, but they'd often drown before they reached the place in the Rift where they could pass through, so the Qik developed technology to turn people into mermaids so they could follow them into the depths of the sea. The big pearl thing we found must've been a malfunctioning remnant of that technology. But there should be a way to reverse it. Hopefully."
"Great." Ianto groaned, letting himself sink into the water so just the top of his head was sticking out, and causing his new tail to snake down onto the floor. 
There was the sound of a door opening down the hall and a low meow.
"HERMES!" Gabby's voice exclaimed as the racket of cat paws and a child's feet running along hardwood approached them.
Ianto resurfaced with a yell as Hermes darted into the room and pounced on his tail. The fluffy white cat was soon followed by Gabby, who stopped behind her father with the same awed look he'd had before. Then she beamed and started to jump up and down excitedly.
"I KNEW IT I KNEW IT I KNEW IT I KNEW IT I KNEW IT!" She yelled.
"What did you know, Estrellita?" Sam asked, amused. Gabby stopped bouncing and pointed at Ianto with the most ecstatic expression a six year old girl could muster.
"Papa is a mermaid!"