Before we can swap the children, we must swap the parents.
First, Grimoire Valentine does not die. It's a very near thing, but he doesn't die. It's enough to make Lucrecia rethink this whole Chaos business. She still studies, but decides that maybe prodding the Eldritch with sticks is a bad idea. She seals Chaos away, and sticks to theory, at least for now. Besides, she's pregnant. She has bigger things to worry about.
Vincent steps up and does the honorable thing. Veld, who does not have a young family to worry about, is sent to the mountains. He does not return. Vincent does his best to investigate, but he is distracted by his new duties as Chief. Tally was going to pick either Veld or himself to succeed her, and with Veld gone, Vincent is the only choice. He can't help thinking that he's a fraud, that this role should have gone to his partner and best friend, but he resolves to try to do the best he can since Veld isn't here to do it himself. It's a promise he makes to himself, his wife, and his new son. They name him "Seth", after Lu's father. Vincent doesn't like the direction Shinra politics are heading. He moves his young family to Kalm, where it will surely be safer.
He is wrong.
When Seth is three, the bombs fall. Vincent will forever wonder if the fire was meant for him. It doesn't kill him, but it does leave him broken and scarred. He loses his wife, his sons, and his left arm. Yes, "sons". Lu was pregnant for the second time. Like Veld, Vincent tries to find them, tries to at least obtain their remains, but he is unsuccessful. The four ghosts haunt him all through his tenure, until he sees one of them reappear on an intelligence feed. His heart nearly stops.
AVALANCHE has become a thorn in Shinra's side, constantly sabotaging mako reactors and other corporate expansion. He knows that face. It's his own, framed by Lu's brown hair. He's calling himself "Sephiroth", but that's Seth. He'd stake his right arm on it. Their sources say AVALANCHE is heading toward Corel, to wreck the unfinished reactor being built there. Under any other circumstances, Vincent might let the kids handle it. He's too old to do more than call orders from behind a desk. But this is his son. He is going. Let anyone try to stop him.
Shinra has their own ideas.
Their greatest weapon has recently returned home from overseas. Without her and her brothers in arms, the Wutai War might have gone very differently. General Elfe, the Demon of Wutai, will surely make short work of these upstart eco-terrorists.
Twenty-five years ago, Gast and Ifalna had come home with Hojo, a baby, and not much else. General Elfe was supposed to be the first Cetra to walk Gaia in many millennia. However, she never heard the voice of the Planet. She did, however, prove exceptionally good at killing things. She was put into the military instead, and became the first SOLDIER; the only known female to tolerate the treatments.
She isn't tall or broad like Genesis or Angeal, but she can more than hold her own. There had been a time when others scoffed at her because of her size, because of her gender. Everyone knows better than to laugh now. Her silver-white hair cut boy-short and dressed in a leather jacket that nearly sweeps the ground, only her vibrantly blue eyes provide any color to her look. It is an aesthetic built to intimidate, to serve as a warning. If the hint is not taken, there is always the Wutaian longsword on her back to drive the point home.
Vincent is there to witness the faceoff in the mountains. He wants so desperately to step between them, to call Seth's name, but he is too far away. Perhaps it's just as well. He might make things worse. He thinks about taking aim at Elfe's platinum head. Thinks about at least grazing her to save his son. Fingers the trigger. But then they've drawn steel and are moving too fast for him to track. He could not have taken a shot if he wanted to.
They prove oddly well-matched. Seth has his height, his long reach, and Elfe is freakishly fast and strong. Against all odds, Seth sends her sprawling in the dust. There is a palpable moment of dead silence as she picks herself up, sweeping the dust from her jacket. Seth just stares, as if he cannot comprehend what he's just done. Elfe raises her sword to him and smiles; a salute to a worthy opponent. Rather than slaughter him and his men where they stand, Elfe beckons to hers and retreats. Vincent feels himself wilt with relief.
He surprises him later. Seth catches a glimpse of him on the catwalk above the reactor.
"Dad?" he asks, features an agonizing mix of surprise and disbelief.
Vincent is sure the same look is etched on his own face. Abruptly, Seth crumbles, and his second hurries to catch him. The mission goes to hell shortly after that, but his kids get away safe, and Seth is with him again, and that's really all he cares about. At this point, Shinra can go fuck itself. Repeatedly. With a large, unlubricated object. He has his son again. Nothing else matters. Tseng, bless him, agrees to provide cover, and spread the story of the Chief's death. Vincent passes the mantle to Tseng, giving him what blessing he can:
"Good luck, kid. You're gonna need it."
Seth is disoriented, confused, and justifiably angry. Between the two of them, they piece together what happened. After the fire, Seth and Lu had been treated at Old Midgar General. There, he received a materia shard to keep his severely burned left hand from deteriorating any further. According to Shinra, Lu died before giving birth. Seth has tried to look into it himself, but his access to Shinra's records is limited. As far as he knows, she died of her injuries, his little brother perishing with her before he'd ever had a chance to live. As a memoriam, they name him "Nero", after Vincent's grandfather. It's something.
Seth holds the hand with the materia up to Vincent's prosthetic left hand.
"You know it's killing me," he says.
There are four shards total. One is not enough, he needs all four to keep stable. His tactician had some ideas as to where to find them. Vincent resolves to find them all or die trying. They already have one shard, courtesy of the second, Shears. The tactician, Fuhito, points them north: Nibelheim.
To be honest, Vincent smells a set-up. Paranoia has kept him alive this long, and he doesn't see any reason to stop being suspicious of everyone and everything just because he's listed as "killed in action". However, he's long wanted to examine the old Shinra mansion himself. The lab is in the basement, and he and Seth go down, down, down the stairs to where this thrice-cursed mess started. It's not the lab they need to examine.
The crypt had been used as an ersatz storage area for things that would not be affected by the mold of dry bones: paperclips, glass beakers and bottles, mops and brooms, and other generic office supplies. There is a fresh seal on one of the coffins, which suggests it's the one they want. The others are in a state of significant disrepair. This is the only one that's truly intact. Between the two of them, they chip away at the lead. Seth lifts the lid and Vincent barely manages to repress a shout.
It's Veld. Oh dear gods, it's Veld. Vincent sinks to his knees beside the coffin, unable to tear his eyes from the gray, scarred face. The reports were true, then. Killed in action. He starts as a hand comes to rest on his shoulder.
"Dad?" Seth asks. Vincent takes a deep breath and tries to pull himself together. He doesn't have much success.
"That's your Uncle Veld," Vincent tells him, voice strangled to the barest whisper by his held tears. "He was my partner. My best friend. He should have been Chief, not me."
"Dad...it wasn't your fault." Despite calling him 'dad', this is the first tenderness Seth has shown toward him.
iYes it is,/i Vincent thinks. iIt should have been me./i
But his son is still breathing, standing here next to him, alive and ill and they need to do something about that. There is a faint glow coming from beneath Veld's clasped hands. With long fingers nimble as a thief's, Vincent extracts what they've come for: the third Zirconiade shard. Seth lowers the coffin lid and they both stand silent for a moment. In his head, Vincent chants a sutra to guide Veld's soul to the Lifestream. Beside him, Seth does the same. He does not know the details, but it's closure of a sort. He can stamp Veld's file as "Case Closed" and file it away to be buried as well. He asks Tseng to alert him if Nibelheim ever comes up again. There are things buried there besides Veld.
Finding the fourth shard causes something of a fiasco. Evidently the tactician had ideas of his own. Seth and the kids are able to overpower him, but it's a very near thing. Fuhito dies, Seth lives. Mostly. Vincent takes him home, such as it is. Seth is ill enough to allow this. They build something more like a friendship than father-son. Vincent will take it.
Tseng contacts him. Shinra has sent Elfe to Nibelheim, ostensibly to investigate the old reactor. Tseng is reasonably sure this is not the only reason. He smells a set-up, but for what purposes, he doesn't know. Vincent looks at Seth.
"You up for a road trip?"
Seth nods. He is.