This was originally published in Enemy of my Enemy, but it belongs over here.

This takes place before Enemy of my Enemy, and introduces a few elements that come to play in that story.

Brain Trust: A prequel

Winter 2016

The wind was cold, biting into her skin as she stood on the roof of the Shatterdome, but she welcomed it. She needed a moment to gather herself. To embrace the silence after the overwhelming noise of the well-wishers inside. Sometimes, it surprised her how many friends she'd made while she and Donnie worked to get Shell Shocker ready to deploy. Friends were something she'd more or less given up on when she'd accepted the guys into her life.

She sighed, wrapping her arms around herself, and her birthday gift — a flight jacket with Mikey's newly-approved Shell Shocker logo proudly emblazoned on the front — kept out the worst of the chill.

They meant well. But in the over three years since the Kraang had strapped her into that machine, sometimes her head started getting very… crowded. She breathed in slowly, letting it go as she tried to figure out where April began and ended.

"April?"

Of course it's him.

Taking another steadying breath, she turned with a smile. "Hey, Donnie. Sorry, I'm not being a very good birthday girl, am I?"

"No, no, I understand," he said, fidgeting a little. "It's just…." He reached into the pocket of his own flight jacket. "There wasn't really the right opportunity to give you this."

Her eyes widened as he pulled out a suspiciously small velvet box and held it out to her. She took it, her hands trembling as she fought against what she suspected was inside. "Donnie, you shouldn't—"

"Please, April," he said, and his voice was taught with nervousness. "Just… open it."

Donnie, I swear to god, if this is a ring, I'm going to….

But as the box opened with a little creak, her breath left her in a rush and the thought died unfinished as she stared at what the box contained.

The pendant lay nestled against dark velvet, shining like a small star in the glow of the searchlights that swept the bay for signs of kaiju. It was Mikey's Shell Shocker logo done in miniature, the shell carved of pale jade, each scute lovingly picked out in minute detail. The lightning bolt blazed across the shell in gleaming gold, supporting the golden circle that bore the four coloured gems at the cardinal points, one stone for each turtle.

She ran her fingers over it in mute shock. She had never really been one for jewellery, but this… this was perfect. And it didn't take a genius to figure out who had made it. "Donnie, I—"

"They think that insignia is all about us," he said quietly. "The shell. The colour points. But there's a fifth member of the family in there — Mikey made sure of that. The fifth pilot. The one who looks out for us and keeps the rest of us together." His fingertip brushed against the gold circle, and his dark eyes were solemn as they met hers. "Without you, we'd still be in those cages in that lab. A jacket… it wasn't really enough to say thank you for that."

His earnest face wavered and blurred, and she didn't trust her voice to answer. Instead, she turned her back to him and lifted her hair in silent invitation.

It took him several tries — the tiny clasp wasn't designed for turtle fingers, but he got it in the end. Donnie, after all, had very, very clever hands. And as the tiny shell came to rest just below the hollow of her throat, she let out another long breath and envisioned a wall around her mind, circling it like a protective gold ring.

And suddenly, blissfully, all the voices in her head fell silent.

"Did… did you wanna go back?" Donnie asked hesitantly.

In answer, April let herself lean back, coming to rest against the solid wall of his plastron. He jumped a little at that, and she smiled as she shook her head. "If it's okay, can we just stay here a while?"

After a moment, Donnie cleared his throat, and to his credit, there was only a tiny squeak in his voice when he answered. "Sure thing! You're the birthday girl."

But after that, he was silent, his arms coming around her from behind to keep the cold at bay as she closed her eyes, content in the knowledge that he understood. He was perfectly happy to just let her enjoy the silence. More than anyone else in the world, he understood just how long it had been in coming.

Summer 2017

The cybernetic circuitry of the thinking cap clung to him, and though he knew that the sweat currently pouring down his face wouldn't short it out, he fervently hoped that it would. He wanted something — anything — to go wrong before this test was allowed to reach its conclusion.

Drift compatible. He and April tested off the charts. He knew that. But up until this point, there'd always been something to put it off. He was needed to fix some complex piece of equipment, or April was needed to analyze kaiju movement patterns.

But now Takahashi had put his foot down. Quantum Bravo was just sitting in the bay gathering dust, and they needed another strong team to take the Mark II out. So here he was, wired into the pons next to April and praying for the sky to fall.

Neural bridge initiation in three…. two…

There was a flash of light, and klaxons began to scream throughout the Shatterdome. The synthesized voice of the AI aborted the countdown, and began a new pattern.

Movement detected in the Breach. New York seaboard trajectory confirmed. Shell Shocker, report for drop.

"YES!" Donnie shouted, pumping his fist. Only then did he remember that he wasn't alone, and met the stunned gazes of his family. "Uh… I mean… boo?"

With a whoop, Mikey jumped from his perch on a control panel and darted past. "Leo, my man, we're up, bro! Let's dance!"

Leo followed Mikey quietly, shaking his head as he passed. Raph was close behind Leo, but paused next to Donnie, and Donatello couldn't help but flinch as the intensity of Raph's gaze met his.

"Get it together, Donnie," Raph said, looking after Leo's retreating back. "We need another team out there. We can't let 'em carry it alone." His expression hardened. "Especially him."

With that, Raph followed after their brothers, leaving Donnie and April to be freed from the circuitry suits by the waiting ground crews. Donnie glanced over at April, meeting her questioning look with a sheepish shrug, but he said nothing.

How could he admit that he was afraid to let the person he was most drift compatible with see what was in his head? And that he was even more afraid to see what was… or wasn't… in hers...