The following week was a whirlwind of focused, intense preparation. Their shared office became a war room, the walls covered in Hermione's complex charts and Cassian's intuitive, swirling diagrams. The fracture in their partnership had not just healed; it had forged something stronger, a seamless blend of her method and his instinct.
They worked late into the evenings, fueled by endless cups of tea and a shared, singular purpose. The easy camaraderie from the late-night vigil returned, but now it was filled with a new, electric energy. They debated, but it was productive, a rapid-fire exchange of ideas that often ended with one of them seizing a quill to scribble down a breakthrough.
"The probe can't be visual," Cassian argued one evening, leaning over her shoulder to point at a line in her runic sequence. "A scrying charm would be too aggressive. It has to be purely empathic. A thread of feeling."
"But how do we quantify the data?" Hermione asked, tilting her head back to look up at him. He was close, close enough that she could see the faint stubble along his jawline and the different shades of grey in his eyes.
"We don't," he said, his voice low and intent. "We don't quantify it. We experience it. We interpret it. Like we did before." His eyes flickered down to her hand for a fraction of a second, and the memory of their joined hands, the shared grief, passed between them unspoken.
Hermione swallowed. "That's… not very scientific."
"It's a different kind of science," he countered, straightening up. "The science of the soul."
They finally had their plan. A single, hair-thin filament of magic, woven from a spell of pure intent and curiosity, designed to slip through the fracture in the Vault's stasis field, feel what was on the other side for a mere three seconds, and then retract. They had seventeen different containment and severance charms ready to activate at the first sign of trouble. Hermione had even convinced Kingsley to have a team of Aurors on standby outside the chamber, though she hoped with every fiber of her being that it wouldn't be necessary.
The day of the attempt dawned cold and grey. The usual Aurors at the dungeon door were replaced by two senior members of the Hit Wizards, their faces grim. The air crackled with tension.
Inside the chamber, it was just the two of them. The Vault hummed its usual, low song, oblivious to the delicate surgery they were about to perform.
"Ready?" Cassian's voice was calm, but she could see the pulse beating rapidly at the base of his throat.
Hermione took a deep, steadying breath, her wand held in a white-knuckled grip. "Ready."
He nodded. He was to cast the primary thread, his magic being more attuned to the Vault's subtle frequencies. Hermione's job was to maintain the containment field and be ready to sever the connection.
Cassian closed his eyes, centering himself. When he opened them, his gaze was clear and focused. He raised his wand, not in a sharp jab, but in a slow, fluid motion, as if painting in the air.
"Ausculto Cor," he whispered. (I listen to the heart.)
A thread of silver light, so fine it was almost invisible, emerged from the tip of his wand. It moved with a life of its own, weaving through the air towards the Vault, towards the tiny, pulsing flaw in its matrix. The air grew colder. The hum of the Vault seemed to hesitate.
Hermione held her breath, her own wand raised, her entire being focused on the delicate balance of the containment spells. She could feel the immense power of the Vault pressing against her magical barriers, a sleeping giant disturbed by a pinprick.
The silver thread touched the fracture.
For a second, nothing happened.
Then, the world dissolved.
It wasn't a vision. It wasn't a sound. It was a pure, overwhelming wave of feeling that flooded the chamber, bypassing their senses and pouring directly into their souls.
Desolation.
A loneliness so vast it stretched across eons. The agony of a final, eternal separation. It was the grief they had felt before, but magnified a thousandfold, a raw, screaming wound in the fabric of reality. It was the sound of a universe where only one heart was left beating.
Hermione gasped, her knees buckling. She felt Cassian stagger beside her, a low groan escaping his lips. The emotional torrent was physically painful, a weight crushing her chest.
But beneath the grief, just for a fleeting moment, she felt something else. A love. A love so fierce, so profound, it had been strong enough to build this entire magical tomb around its own absence. It was the love that had nowhere to go.
Three seconds.
The thought was a desperate scream in her mind. Sever it!
She tried to raise her wand, to speak the counter-charm, but her body wouldn't obey. She was drowning in someone else's sorrow.
Then, she felt a hand clamp around her wrist. Cassian's. His grip was iron-strong, anchoring her. Through the torrent of shared despair, his presence was a lifeline. She felt his magic surge, not to fight the Vault, but to join with hers.
"Now," he ground out, his voice strained.
Together, their wands moved. "Praecido!" they shouted in ragged unison.
The silver thread snapped.
The connection severed with a silent, psychic shockwave that threw them both backward. Hermione landed hard on the stone floor, her head spinning, her body trembling uncontrollably. Cassian was on his hands and knees a few feet away, breathing in ragged gasps.
The chamber was silent. The Vault hummed on, unchanged, its secret sorrow once again locked away.
Hermione pushed herself up onto her elbows, her vision swimming. She looked at Cassian. His face was pale, his eyes wide with the echo of what they had just experienced.
They had asked their question.
And the Vault had answered with a scream of loss so absolute it had nearly shattered them.
Slowly, shakily, Cassian got to his feet and stumbled over to her. He didn't offer a hand. He just sank down beside her, his back against the cold wall, his shoulders touching hers. It wasn't a romantic gesture. It was a necessity. Two survivors clinging to each other in the aftermath of a storm.
For a long time, neither of them spoke. They just sat there in the profound silence, breathing, feeling the ghost of that ancient grief slowly recede.
Finally, Cassian turned his head, his face inches from hers. His stormy eyes were dark with shared trauma, but also with a burning, triumphant light.
"It's not a monster," he whispered, his voice hoarse. "It's a monument."
Hermione could only nod, her throat too tight for words. They had gone looking for a threat and had found a tragedy. And in doing so, they had shared a burden so heavy it had irrevocably tied their souls together. The work was no longer just a project. It was a quest. And they were the only two people in the world who understood why.