"Has the Mer been acting weird lately?" Sirius murmurs to Remus as they slowly circle together quite a bit above their trench, looking down the gap in the forest to where the Mer is still lying on his stomach even though he seemed to prefer to curl up when he sleeps.
"He doesn't talk anymore unless I ask a question," Remus admits. "You don't think he's sick, do you?"
"His tail isn't bleaching," Sirius points out. "No, I think he's just acting suspicious. I saw him with extra seaweed yesterday and when I snatched it back he didn't even get mad, just lay there."
"I thought you were feeding him more," Remus says in shock.
James is still recovering from injuries, and he's never going to recover from a torn tail fin, but he has been looking healthier lately. Remus thought Sirius was just taking pity on the Mer.
"I think he's slipping out of the chain when we aren't looking," Sirius admits.
"He'd be long gone if that were true," Remus points out.
Down below, the small figure of the Mer shifts a bit, looking around. He looks straight up but in this darkness he can't possibly see the Sirens with Mer eyesight. James shuffles a bit and a shadow darts out and into the forest. Sirius and Remus both come to a halt and watch.
The shadow is barely seen zipping between seaweed, dragging food back to James before vanishing again in a blur. It comes back with something else this time and starts in on the shackle around James' tail.
"How did Harry get here?" Sirius asks in amazement.
"Is that a Mer kid?" Remus asks in shock.
Sirius gestures down. "Well there you go, that's why James is acting weird. Come on, I want to introduce you to Harry."
They swim down and as they get closer, the Mer kid startles and James quickly rips the kid away from the shackle and shoves him into what the Sirens now realise is a hole in the sand under James.
"Harry!" Sirius cheers as he comes to a stop floating over James. "Hey, how have you been?"
James struggles but Harry tucks a head over his shoulder and hisses angrily.
"Don't be like that," Sirius tsks. "It's nothing personal. I mean look how nice we've been treating your dad."
"Let him go!" Harry cries. "You have more than enough food anyway."
"That?" Sirius gestures at the weaved net stuffed full. "That's going to last us a week tops and nothing is coming for James anymore so we're going to be running low very soon." Which is true but also a lie. Both Sirens have bulked up and they can last on the stored energy for at least a month without needing to eat again though it would be uncomfortable.
"Harry – Harry stop!" James tries but the kids is fast and slippery and James doesn't want to hurt him.
Harry bursts back up and floats high enough that when James tries to straighten up he still can't reach.
Harry scowls down at Sirius. "If I beat you in a fight, you'll let dad go."
Sirius turns to Remus with a raised eyebrow, nods towards James.
Remus rolls his eyes. "Okay, fine, how about this? We bleed James one more time and then we let both of you go."
"No!" Harry snaps. "You're not hurting my dad anymore!"
"Harry!" James hisses, grabbing for a tail until he can reel the boy into his chest. James glances warily between the two Sirens. "You let Harry go first and then we can talk."
"This isn't a trick," Sirius soothes. "We were talking about letting you go anyway."
James is -understandably- incredulous.
Remus shrugs a bit sheepishly. "You've grown on us."
"And then that's it?" James asks sceptically. "Nothing more? You let us go and then we never see each other again?"
"Oh we are absolutely eating Mers from your reef, just not you two in particular."
James pauses. "If I stay, will you not bother the reef anymore?"
Harry looks up at James in horror.
James quickly shushes him before Harry can even say anything. "No, look, just…" He turns to the Sirens. "There's a big…a thing soon. One large meal in return for you never coming back."
Remus and Sirius share a glance. They don't often go near the reef but they do steal fish sometimes, snatch away a Mer or two who stray too far at night. Losing an easy source of food might not be worth it.
"We'll get back to you on that," Sirius says.
James sends Harry off when it happens – with Sirius actually because James hates to admit it but Harry will be fine with the Siren. They've cracked open the shackle already, and it took both Sirens to do it so yeah, James was not getting that off no matter how much will power Harry put into it.
James settles into the sand of the small nest he made (took over) and Remus splits open the meaty part of James' tail with a long claw, over a hip and part way down, somewhere quick to heal and won't get in the way of normal life too much.
James grits his teeth and breathes through it.
Even as a Mer, obviously Harry can smell the blood when it's so close by, but Sirius takes him on a tour of the place and distracts the kid as best as he can. He does eventually need to dump Harry back off with James because the predators are coming in and Remus might need help dealing with it.
James and Harry curl up together in the nest and Harry very bravely comforts James and tells him all about the Siren fight that neither of them can see but can definitely still hear.
James is pretty sure Sirens can't shoot scales out of their tail but Harry gets full marks for creativity.
While James had been here, Remus and Sirius took turns sleeping in the forest, but Sirius decides it's fine now and just sleeps directly next to James in the nest, probably keeping the Mer up with how he's chatting to Harry about all things Siren.
Harry is a curious kid and now that he's certain he saved his dad, he's asking all the questions he's kept inside until now. Remus is happy to take on the more technical questions.
The Sirens used to travel a lot before, so they describe the different sea creatures they've seen. The Deep Dwellers. Octopus-hybrid Sirens, or eel, one time a particularly odd sea cucumber Siren.
Harry complains about a jellyfish Mer called Snape who billows around the reef and all the kids are scared of him. There's a nice seahorse Mer, and a pod of dolphin-hybrids who come around and act mean but bring a lot of information so Lily lets them in anyway.
James still has to keep interrupting when Harry starts talking about reef business but doesn't mind talking about harmless things like what raising a Mer egg is like, other Siren he's met or the human boats.
Neither Remus nor Sirius believe James has met a human before so they agree to disagree.
Harry starts going out with Remus on patrols and can hear Sirius and James cracking up laughing occasionally. They both have the stupidest stories that James doesn't want Harry to hear and Sirius doesn't want Remus to frown at, so they regale each other with dumb childhood tales.
One time, Sirius wanted to see if he could fit in a whale's mouth. He could.
One time, James wanted to see how deep down he could go. He didn't get far but he did make friends with a giant squid.
Remus clucks around James and Harry, adjusting the net strapped to James' back filled with food for on the way to the reef as well as some nice shells Harry found, and a tooth from the shark Sirius and Harry took down together.
The four of them are doing spins around the small nest, making sure they have everything. It's become quite cluttered with odd things buried under the sand and a border made of nice green scales that Harry has been shedding as he grows rapidly. James dropped some too and the glittering brown ones go in the 'shiny' pile Sirius has started.
"Okay, I think that's everything," James says, adjusting the straps around his shoulders. He's healed up well, not all the way but enough for it to not bother him on the trip back. "Say goodbye, Harry, we should head off soon while there's still lots of sunlight."
Harry hugs Sirius and Remus goodbye, goes back to Sirius for seconds, does a spin of the nest, goes back to Remus.
"Harry," James begins sternly. "Your mum must be worried sick, we can't waste more time."
Harry reluctantly swims over to James who is drifting upwards through the forest. "Um, maybe you can come by later-"
"Don't ever come back!" James interrupts and grabs Harry in a hug, shooting off with slightly awkward aim so his tail brushes the seaweed instead of avoiding it entirely. James pauses though and looks down. "When it gets warmer…I'll get you something, if you won't take from the reef again."
"We agree," Remus says for both Sirens because they'd talked about it, low risk and high reward, and James is very unlikely to trick them so the food will likely be filling.
James nods and takes off.
Sirius sighs as the two Mer swim off into the distance. "Whelp, that was interesting. Anyway, I'm going for a perimeter check."
"Is this perimeter check going to be for two days?" Remus asks pointedly. "In the direction of the reef?"
Sirius throws up his hands. "James can barely swim!"
"He's going pretty fast," Remus argues.
Sirius does and spin in place and frowns at Remus. "Fine, maybe I'm going to escort them home."
"Just wanted to confirm," Remus says casually and starts swimming upwards. "Let's go, I want to see how fast Harry can get in open water."
Sirius stares after Remus. "You just - you were going anyway?!"
Over the course of his stay, James learned many things about Sirens.
He learned too much sunlight hurt their eyes so he swims with Harry at the surface. He learned they can see much further than Mer and have sharper senses so he doesn't try to camoflauge.
James goes fast and doesn't stop, relearns his tail as he goes because it needs a sharper flick now, more power in the tail than the fin, a wider sweep when he turns.
The Sirens also learned about Merfolk so they hang back far enough that James can't see them, stay away from the seabed because Mer have a wider colour range in their sight and can spot Sirius' black on sandy off-white immediately.
They follow after each other for half a day and while Sirens have power, they don't have the stamina of Mers because they tend to conserve energy for larger but fewer meals.
"Slow the fuck down," Sirius wheezes.
"I'm giving up," Remus pants, starting to slow. "I'll hang back."
"I should have ripped his entire fin off," Sirius complains.
There's a commotion and James slows down. Both Sirens snap into predator mode but Harry breaks away and the two Mer hold hands, starting to swim again but much slower now to accommodate for a tiny kid.
James also moves up much closer to the waves, almost in them, where the sunlight radiates bursts of sudden colour reflecting off the water and helps disguise the two of them better.
The two Sirens go far enough that they can see the seabed start to slope up onto a shelf where the reef is further in and then they swim back to their trench.
The trench seems a lot colder and quieter without two extra bodies.