Chapter Text
Luis knew he was getting himself into something potentially dangerous. That triton Umbrella had captured would never work as a biological weapon—he was far too intelligent, far too rebellious, and, above all, deeply involved with the very scientist assigned to study him. Leon had built himself a nest and decorated it with none other than items stolen from Luis Serra. The researcher could—and probably should—have let it go. After all, every sign pointed to an ovulation period, part of the reproductive cycle of merfolk who, as Serra and Birkin had confirmed, were hermaphrodites. That meant all the passion, jealousy, and possessiveness were temporary.
Or at least they were supposed to be.
Luis and the team weren’t entirely sure.
And yet, he still took the risk.
He befriended the creature, enjoyed himself, and spent long stretches of time with him.
They talked about everything, and Luis had practically moved into the lab—buying a sofa bed and bringing most of his belongings to work for the sole purpose of staying close to the tank and to Leon. It wasn’t as if Umbrella would question his behavior; Serra was the only person capable of calming the triton’s volatile temper, questionable methods included—methods that involved several bags of strawberries and a pet kitten.
Luis couldn’t lie to himself: he was enchanted by that creature.
And he knew the monster felt the same.
That was dangerous. It reinforced Leon’s possessive behavior toward the scientist, making it harder for other researchers to approach the tank—and Serra himself. Luis had been summoned and formally reprimanded by Umbrella’s administration after the Ann Lee incident, when Leon not only tried to attack the lab assistant but also dragged Luis into the water. The scientist promised his superiors he would correct those behavioral deviations.
And, in a way, he had.
His constant presence in the lab and frequent conversations with Leon had tamed the beast.
Leon no longer splashed lab technicians, nor did he seem bothered—at least apparently—when strangers touched Luis. Still, Luis continued to play with fire by flirting with and getting close to the triton. That earned them cooperative behavior during lab exams, but on the other hand, it threatened the integrity of the research and Serra’s own reputation.
He didn’t seem to care.
He’d lost count of how many nights he’d slept curled against Leon’s chest, listening to the triton’s deep purring mingle with Mônica’s—the kitten acting as both guardian and witness to that couple.
“Can you tell me when this ends?” Leon asked one night, full of expectation.
Luis stayed silent. Even he didn’t know how long he could keep stringing Umbrella along and prevent Leon from being transferred to another sector—months had already gone by. They wanted to test his strength, his voice, and his newly discovered ability to mimic—albeit temporarily—a pair of human legs. He drifted into reverie, remembering the day Annette Birkin screamed when she saw the triton leave the tank and, instead of dragging himself along with his tail, walking like a slightly more scaly human. That was the day everyone found out how he’d been stealing objects from Luis’s desk.
“I know you’re not asleep,” Leon insisted, wrapping his tail around one of the scientist’s legs.
“Leon…” Eyes closed, Luis hesitated. He didn’t want to tell the truth and ruin their romantic moment at the edge of the tank, but he couldn’t lie for long—not when the merfolk already regarded him as a mate.
“Please,” Leon felt Luis’s hands stroke his neck, a sensitive spot reserved only for a partner. “I don’t know what you want from me anymore. I can’t stand swimming in circles, and I miss home… This isn’t the first time I’ve asked you and you act like this.”
“Like what?” Serra didn’t understand.
“Pretending to sleep while you run your fingers through my gills so I’ll fall asleep too.”
Luis opened his eyes at once, a faint panic shaking his chest, as if Leon had cornered him. He lifted his head and met a pair of tired, hopeless eyes. It was clear Leon already knew the answers—he just wanted final confirmation.
“Please… Will I ever be able to leave here?”
“Little fish…” Luis sighed, unable to look at that desolate expression for long. “You’re never leaving this place.”
A heavy breath shook the triton’s chest as Leon sat up abruptly, nearly knocking Luis from his support.
The researcher didn’t have time to react; he only caught the moment Leon dove back into the tank, swimming sadly toward the bottom. Luis couldn’t blame him—this lab was the only environment the creature had known for months, most of that time spent in a single room, inside a tank designed to be a massive aquarium. Defeated, Dr. Serra walked to the platform’s edge and watched Leon’s trembling figure curl up, lying tightly coiled at the center of the nest made of stones, algae, and objects from Luis’s work desk.
A sad meow pulled him from his stupor as Mônica rubbed her head against his ankles.
“Yeah, little friend,” he crouched and gently scratched behind the cat’s ears. “Leon isn’t the only one trapped here.”
Mônica kept weaving between his legs while he absentmindedly stroked her, as if trying to distract himself from the inevitable despair of the curled-up shape at the bottom of the tank. The calico kitten—almost entirely orange—eventually tired of the affection and padded away from the platform, returning to her bed and leaving the researcher alone again. He took that as a sign to stand and head for the sofa bed.
Descending the platform stairs and walking toward the office, Luis considered sleeping at home that night—giving Leon and Mônica some space, choosing to distance himself from the inevitable: he had no power to get Leon out of there.
He was gathering his lab coat and looking for his car keys when a beautiful voice stopped him.
A deep, soft, enchanting voice.
A siren’s song.
Leon was singing again.
It was rare—usually it only happened when Luis was around.
But there was something different about this song.
Luis was fully aware and in control of his senses, yet little by little he noticed something in that melody urging him to act, and he found himself walking toward the tank. He knew exactly what was happening; he even remembered joking with Leon, asking if he’d ever lured someone into the water with his voice and drowned them. If there was any way to resist the triton’s charm, Luis chose to ignore it.
He approached the aquarium. There was Leon, water up to his chest, arms open and gesturing sensually, singing for Luis to come closer.
"My lonely thinker,
Come with me.
My lonely thinker,
Let the sea wash away
All your agony.
Come.
Come with me."
It was too much. Luis stopped at the platform’s edge, hypnotized.
Leon swam toward him, and when he surfaced, Luis realized where the whole ritual was leading.
And he had already chosen to give in.
“Leon,” Luis held out his hand. “Grant me the honor of being your mate.”
A smile of satisfaction and desire spread across Leon’s face as he reached out, pulling Luis into the tank.
Yes, he would yield to the siren’s desires.
In truth, it would be unfair to say the desire was only Leon’s—Luis himself had been holding back for a long time.
Their lips finally met, relief spilling out in their moans.
There was no time to breathe; Leon was insatiable, strong arms pulling Luis close, eliminating any chance of escape. Not that Luis complained. He didn’t mind when the triton’s claws tore his shirt. Their lips parted only briefly before meeting again, just long enough for Luis to rid himself of his pants. He kissed Leon’s chin, feeling the triton’s human legs, frantic feet tugging at his underwear.
Luis Serra Navarro’s career as a researcher for the Umbrella Corporation ended right there, when he shed all modesty and joined himself to Leon. Now physically united with the triton, Luis unconsciously renounced a life of academic prestige and technological advancement in the name of an intense passion for what should have been nothing more than another biological weapon.
+++
The months that followed passed naturally.
When it was all over, Luis made sure to bribe the camera operators with a generous sum to erase the footage from that night—and those that followed.
At the same time, research on Leon continued to progress.
The triton now left the tank voluntarily, perfectly capable of walking on land by mimicking human legs—this time indefinitely. His aggression toward staff disappeared, and he began physical combat training. He was taught how to handle weapons and shoot, outfitted with combat gear adapted to his shape-shifting, now amphibious, and—most importantly—trained to use his voice as a stunning weapon.
Still, one small detail troubled the researchers.
A detail Luis conveniently ignored.
Leon’s latest blood tests showed elevated levels of estrogen and prolactin, and over six months of training he hadn’t entered his monthly hormonal cycle, as he had at the start of the program. He also showed an increased appetite, though that could be explained by constant physical activity, in and out of the water. Annette Birkin was already suspicious of Luis’s excessive leniency and closeness to the triton, but unwilling to hurt her friend, she kept her doubts to herself and waited before drawing conclusions.
She didn’t want to judge—or assume—that Luis would cross such a delicate line between species.
But the siren’s behavior proved Birkin right.
It was supposed to be another calm morning at Umbrella’s facilities.
Leon, still in his typical form, swam idly around the tank while Luis and his assistant, Ann Lee, took turns observing and taking notes. At some point, Dr. Serra asked Ann to fetch him a coffee, and when she handed him the cup, he made the mistake of thanking her with a kiss on the forehead.
What followed stunned them both—and triggered alarms.
A guttural roar followed by a piercing, deafening scream erupted from the tank.
The coffee spilled onto the floor as Luis and Ann clutched their ears, dazed by what they heard and saw.
Leon was no longer the beautiful triton or prince-like man, but a monstrous beast—half man, half fish—with sharp teeth and claws, and a mouth whose jaws split in two as it screamed instinctively, as if something had invaded its territory.
“Leon, my little fish!” Luis shouted, hands over his ears. “What are you doing?”
There was no verbal response. Driven by a bestial impulse, the monster began slamming against the acrylic tank. Curled on the floor in terror, Ann sobbed, afraid the sound would shatter her skull. She shut her eyes, feeling the creature’s hatred and screams directed at her, Leon’s voice echoing telepathically in the back of her mind:
“He’s mine! Don’t you dare touch him!”
Luis, meanwhile, tried to approach the tank, still not understanding what had sparked Leon’s fury.
“Doctor, he hates me!” Lee’s crying cut in. “Please, get someone to take me out of here!”
That was when the gears began to turn in Serra’s mind.
“Pececito!” he pleaded, using the Spanish nickname, and for a moment caught the beast’s attention. “Don’t be like this—she’s a friend, don’t you remember?”
Leon stopped screaming for an instant, and the pressure in Luis’s—and especially Ann’s—head eased. The triton’s face shifted back to a more human aspect, closer to what everyone knew. Luis approached the cracked tank again.
“That’s it, mi Pececito.” Serra placed his sweaty hand on the glass. “There’s nothing to fear. Everything’s fine, I—”
The calm didn’t last long. Other scientists and the Containment Team rushed into the lab as the alarms blared after the biological weapon’s collapse. Leon grew agitated again, adopting a defensive posture, but he didn’t open his mouth to scream—he realized Ann wouldn’t be the only one whose head his voice could shatter. He would never forgive himself for killing Luis that way.
“Subject 246 has exhibited elevated stress levels and poses a threat to researcher safety,” Annette Birkin said, leading the group. “Dr. Serra, can you explain what’s going on?”
“Annette,” Luis hurried to justify himself, “Leon just had a minor mood imbalance. I’ve already handled it—”
“That’s not what the footage shows,” Birkin cut in coldly.
“Doctor—”
“Dr. Serra, I’ve reviewed your reports and have sufficient grounds to confirm that what just happened is a symptom of something more delicate—something you haven’t been paying attention to lately.”
“What are you talking about?”
“The tests,” she went straight to the point. “Subject 246—self-identified as Leon—has higher-than-expected levels of female hormones.”
“But that doesn’t affect his training performance—”
“Don’t interrupt me!” The veins in Annette’s neck bulged. “Beyond hormones, 246 shows friendly behavior toward the staff, but this only occurs after long periods of isolation alongside the scientist responsible for his domestication.”
“Where are you going with this, Annette?” Luis narrowed his eyes.
“I want to perform an ultrasound on 246,” Birkin continued, cold and precise. “What happened today wasn’t a simple imbalance—it was the manifestation of territorial, and I would even say maternal, instinct.”
The words died in Luis’s throat as his blood ran cold.
“The Containment Team is ready to remove him from the tank, and the subject will be sedated if he resists. Don’t worry, Dr. Serra—246 will be safe,” her expression softened briefly. “We just need to ensure there’s no compromise to our research. You understand, don’t you?”
Luis sighed in defeat, shoulders slumping.
“At least let me go with him,” he said without waiting for permission. “If you want this over quickly, Annette, it’s best to keep him calm. That—or you can take Mônica instead.”
Annette considered it for a moment before answering:
“Between you and a cat in love with water, I’m forced to give in.”
+++
It didn’t take long to remove Leon from the tank. At first, the triton resisted, but he didn’t attack the team, choosing instead to hide among the rocks and evade the divers. His hunched shoulders and curled posture betrayed his regret over losing control, avoiding eye contact with the Containment staff—or anyone else present, including Luis. The researcher stared at the floor, heart pounding, torn between fear of inevitable punishment and dread of what they might do to his beloved.
The Containment Team waited patiently until Leon stopped hiding and surrendered voluntarily. He didn’t protest when the large fishing net enveloped him—unlike when he’d been captured somewhere in the North Atlantic—and waited calmly as they transferred him to a gurney, freeing him from the net.
Luis watched helplessly as the scientists bound Leon’s wrists and tail to the gurney and fitted a kind of muzzle around his mouth.
“Is all of this really necessary?” Luis asked, judging the restraints excessive.
“Safety protocols,” one of the guards replied.
Once the triton was fully restrained for the exam, Annette called out to Luis:
“Prince Eric, I’m not waiting all day!”
Murmuring a short prayer in Spanish, Dr. Serra followed them, asking forgiveness for his profane acts and, above all, begging protection for Leon—and whatever was inside him.
In the ultrasound room, all suspicions were confirmed.
As Annette moved the scanner across Leon’s abdomen, the sound of tiny heartbeats quickly filled the room, making the triton draw in his tail—or what little of it was free. Luis wanted to jump for joy, but fear and Annette’s dry stare—along with the silent judgment of the rest of the team responsible for 246—kept him frozen.
“That is clearly an embryo,” Birkin said, moving the mouse over the monitor to highlight the small shape inside Leon’s bicornuate uterus. “He’s pregnant.” She turned to the triton as if speaking about a cow.
No one spoke for a long while. Eyes avoided one another—and the screen.
“Dr. Serra,” Annette lifted her chin toward Luis.
“Yes?” he tried to maintain composure, despite his sweaty hands on the counter.
“I need the reports.”
“The reports?”
“The latest test results, Luis,” she was firm. “If you don’t want to hand over the paperwork now, fine. At least tell us what you’ve discovered so far about the specimen’s condition so we can proceed with appropriate care during the pregnancy.”
For a fleeting millisecond, Luis caught a glimpse of compassion reflected in Annette’s cold eyes. It gave him hope they wouldn’t harm Leon—or the… offspring. Gathering his strength, he sighed.
“Dr. Birkin, here’s a brief summary of the research conducted between November 1997 and August 1998,” he forced himself to sound mechanical. “Subject 246—self-identified as Leon—biologically presents as a mammal, a hybrid between a human, Homo sapiens sapiens, and a cetacean from the Odontoceti group, though no direct correlation has been found with existing whale or dolphin families.”
“We already know that,” Annette snapped. “Don’t be verbose.”
“Understood.” Reprimanded and knowing he couldn’t stall, Luis let the skeleton out of the closet. “The hybrid—commonly understood as a mermaid or triton—has a reproductive system capable of producing both female and male gametes. Similar to female primates, 246 has a monthly cycle involving ovulation and menstruation, alongside a 24-hour cycle typical of males.”
“And what happens during this cycle?”
“During the fertile period, the siren builds a nest and seeks a partner for reproduction.” Serra felt Annette’s gaze bore into him. “Conversations with 246 revealed the species is predominantly monogamous, and courtship rituals may be performed by individuals of either sex. In addition to nest-building, the siren uses its voice to attract a mate until copulation. The subject uses his voice in various contexts, sometimes resembling a whale, sometimes a human. It’s impossible to determine which vocalization is used to attract partners of his own species.”
“And in the case of a human partner?” Birkin pressed.
“The human voice was used.”
Luis paused. Everyone already knew who Leon’s human partner was. Still, the report wasn’t finished.
“Dr. Serra,” Annette said, “we need to estimate gestation time. When did fertilization occur?”
“All right…” Breathing heavily and avoiding Leon’s gaze, Luis addressed the room. “The first mating occurred in mid-February.”
“Six months of gestation,” she noted. “Apparently, there’s nothing wrong with the embryo. The pregnancy isn’t fully visible yet due to the slow development typical of cetaceans.”
Indeed, the changes were subtle. Leon had a slight protrusion in his lower abdomen and a modest accumulation of fat along his tail and torso, still hidden beneath muscle. Luis also noticed how embarrassed the triton looked, staring at his own belly with a mix of fear and curiosity.
“Do you need anything else, Doctor?”
“No,” she said, packing up the ultrasound equipment. “The team is dismissed—except you, Serra. We need to talk.”
Luis swallowed hard and waited until the others left.
Once they were gone, Birkin released the triton from his restraints and, in a more careful, gentler tone, added:
“Leon, you need to hear this too.”
Stunned, Leon exchanged a glance with Luis, only to see the same confusion reflected there at Annette’s sudden shift in demeanor.