Timeline From Here On Out - Early S3
The air in Princess Bubblegum's main laboratory hung thick with the acrid scent of ozone and burnt sugar. Wires dangled like forlorn vines, shattered beakers glittered across the floor, and half melted contraptions lay slumped against the walls. A recent experimental mishap had turned the usually pristine space into a chaotic, sticky disaster zone.
"Glob, PB, what was that stuff?" Finn coughed, swiping a sticky pink residue from his arm as he wrestled a bent metal beam. He was trying to be helpful, but the sheer scale of the mess was overwhelming.
Princess Bubblegum, her hair slightly singed at the ends, zipped past him on a pair of motorized rollerblades, clutching a complex diagnostic tool. "A highly unstable new compound for enhanced gum elasticity! It turns out 'enhanced' meant 'explosively enhanced.'" She chuckled nervously, a bead of sweat trickling down her temple. "You know, for science!"
She paused, spotting Finn struggling with a particularly stubborn goo covered lever. "Oh, Finn. Where's Jake? His stretching abilities would be quite advantageous right now."
Finn grunted, finally prying the lever free with a squelch. "He's with Lady, PB. Said something about 'Rainicorn family brunch' and 'mandatory awkward small talk.'" He shuddered. "Sounded kinda stressful, TBH."
"Hmm, yes, family gatherings can be… stimulating," PB murmured, already scanning a sparking conduit. "Just try to organize the scattered components into those marked bins, alright?"
Finn nodded, pushing a pile of sizzling green sludge with his foot. He started to meticulously sort twisted wires and smoking circuit boards. His hand brushed against something smooth and cold amidst a pile of crystalline debris. He dug it out.
It was a crimson red box, made of a dark, polished wood, intricately carved with swirling, almost demonic patterns. It felt strangely ancient. Curiosity piqued, he lifted the lid.
Inside, nestled on a plush red cushion, was a single, dim red orb. It pulsed faintly, like a tiny, dying heart, casting a weak, flickering crimson glow on the cushion. It felt warm, strangely comforting, in his palm.
"Woah," Finn breathed, holding it up above his head with both hands. "PB, what's this?"
Princess Bubblegum, who had been meticulously calibrating a large, shattered generator, froze. Her head snapped towards Finn, her eyes wide with a sudden, palpable shock that made her normally unflappable demeanor crack. Her face went pale, almost translucent.
"Finn! Where did you find that?!" Her voice was sharp, a rare edge of panic in it. She rushed towards him, then stopped short, a strange mix of fear and desperation in her expression. "Just… hold onto it for a bit, okay? It's...it's very important. Just keep it safe for me while we clean. Don't… don't open it again."
Finn, sensing the unusual gravity in her voice, nodded slowly giving a salute. "Okay, PB. Got it." He carefully tucked the crimson box into his trusty green backpack, feeling the faint warmth of the orb against his back.
He wandered off, picking up stray pieces of scientific equipment. The lab was bigger than it seemed, with various sections branching off. He found another particularly messy corner, where a workbench had collapsed, spilling more mysterious liquids onto a section of the floor that looked strangely… unstable.
"Man, this is gonna take forever," Finn muttered, stepping onto the damaged floor.
Without warning, the weakened floorboards beneath him gave a loud CRACK! The world lurched, and Finn felt gravity seize him. He yelled, tumbling through the sudden hole, landing with a splash in a dim, cool chamber below. He scrambled to his feet, shaking off the liquid.
He was in a cavernous, dimly lit space, distinct from the lab above. His eyes adjusted, and then he saw it.
In the center of the room stood a massive, cylindrical tank, filled to the brim with a pale, glowing coolant liquid. And inside, suspended perfectly upright, was a figure. A boy.
He was undeniably a demon, with lean, muscular limbs and unmistakable black hair. Two distinct red horns curved from his forehead. His skin was a faint, ethereal greyish blue, and a peculiar, dim red orb, identical to the one in his backpack, hovered gently between his horns, flickering with an unsettling, faint light. He floated in a state of suspended animation, eyes closed, seemingly asleep.
"Woah…" Finn breathed, pressing a hand to the cold glass of the tank. The sheer strangeness of it left him speechless.
Just then, a frantic voice echoed from the hole above. "Finn! Are you alright? What was that noise?!" Princess Bubblegum clambered through the opening, landing beside him, her eyes wide with alarm. She followed his gaze to the tank, and her face went ashen.
"Finn, no! You weren't supposed to…!" Her voice was strained, filled with a desperate urgency. She rushed towards the tank, her hands pressed against the glass near Finn's.
"PB, who is this guy?" Finn asked, his voice a bewildered whisper.
Princess Bubblegum's shoulders slumped. "He… he's an old friend, Finn. From a very, very long time ago." Her voice dropped to a near inaudible murmur. "He got badly injured… his powers became uncontrollable. He almost… he almost burned the Candy Kingdom to the ground. I had to contain him, seal him away, until I could find a way to fix him."
Just as the words left her mouth, a sudden, blinding CRIMSON FLASH erupted from Finn's backpack. The fabric of the bag instantly charred and disintegrated, revealing the red box. The dim red orb within it suddenly pulsed violently, vibrating with immense energy. It shot out of the box like a bullet, leaving a scorching trail in the air.
The orb zipped directly towards the tank, smashing through the thick glass with an explosive CRACK! Coolant liquid sprayed everywhere, drenching Finn and PB. The orb flew straight through the now shattered opening and embedded itself perfectly into the flickering red orb floating between Cassian's horns, fusing with it in a blinding surge of crimson light.
Cassian's eyes snapped open, blazing with an unnatural, raw energy. His body tensed, then convulsed, and he shot out of the tank, landing silently on the wet floor. His face, revealed in the harsh light, was marred by a jagged, burnt scar running from his temple to his jaw, his expression utterly blank, devoid of recognition. He flickered, his entire form seeming to dissolve into embers for a split second before reforming, a shimmering, unstable outline.
Princess Bubblegum screamed, a sound of panic. "No! Cassian! He's not healed yet! He's still unstable! We have to find him!"
Before either of them could react, Cassian took one unsteady step, then, with another violent flicker, he dissolved entirely into a scattering of crimson embers, vanishing into the shadows of the chamber's unseen corners. The only trace left was the lingering scent of ozone and something ancient, and the horrifying silence that followed.
Silence. A cold, echoing silence filled the hidden chamber beneath Princess Bubblegum's lab, broken only by the drip, drip, drip of residual coolant liquid from the shattered tank. The acrid scent of ozone mingled with the sweet, cloying smell of burnt sugar.
Finn stood drenched, his backpack a smoldering ruin. He stared at the spot where Cassian had vanished, his mind reeling. "What just happened, PB? Where'd he go? Did he just... poof?"
Bubblegum whirled on him, grabbing his shoulders with surprising force. Shaking him violently. "His core, Finn! The one from your backpack! It was a partial fragment of his original Flame Core, the one I managed to extract when I sealed him away! I had it in a contained, trying to find a way to stabilize it, to heal him without risking the complete collapse of his being. It must have sensed its other half!"
She squeezed his shoulders, her voice rising in pitch. "It recombined with the core still embedded in him! But he's not ready! He's not stable! His powers... they could be flipping bonkers man!"
"Bonkers how?" Finn asked, his own heart starting to thump against his ribs.
"He could melt down the entire Candy Kingdom! The ground itself! He could just... burn through Ooo!" PB's voice was tight with desperation. "His internal temperature will be spiking. He won't be in control. He won't even know what he's doing!" She released him, pacing frantically around the broken tank, slipping on the slick floor. "We have to find him before he causes any more damage... or hurts himself."
Finn's hero instincts flared, cutting through his confusion. "Then let's go! He can't have gone far, right?"
"His flicker... he's likely teleporting, uncontrollably, in short bursts," PB deduced, rubbing her temples. "Like an ember blowing in the wind. We need to track the energy signatures, but my lab's systems are fried, and the kingdom's scanners aren't sensitive enough!" She looked around the wrecked lab with frustrated despair.
"Jake!" Finn exclaimed, already pulling out his cellular device. "Jake can stretch super far, he can help us find him! And Lady too, she can fly!"
PB nodded, her mind already racing. "Yes! Good idea, Finn. Get them here immediately. We'll need all the help we can get." She started to cobble together a makeshift energy sensor from the less damaged components.
Finn, already dialing, then hesitated.
Princess Bubblegum looked at him, then let out a shaky breath, her face tightening with a familiar look. Telling Marceline meant dredging up a past she had desperately tried to keep buried, a shared secret that had poisoned their friendship. But the danger Cass posed, the sheer, uncontrollable power that could level her kingdom, left her no choice. Marceline had been there. She understood.
"Finn," she said, her voice strained, a raw edge to it. "There's one more person we need. Marceline."
Finn's brow furrowed in confusion. "Marcy? Why Marcy? You guys always seem kinda... beefy with each other."
PB closed her eyes for a brief moment, swallowing hard. "Because she... she knows him. She knew Cassian from a very long time ago. She's the only one who truly understands his abilities and the unique danger he poses when unstable. She might be the only one who knows where he might go, or how to stop him without... without causing more harm." The words felt heavy, thick with untold history, but she kept the specific nature of Marceline's connection to herself. Finn didn't need to know everything right now. Not yet.
"She... she needs to know." PB added, almost to herself, thinking of Marceline's melancholic song from earlier, a painful ache in her chest. He is her brother. Her baby bro.
Within minutes, Finn had sent a frantic text to Jake, detailing the emergency in rapid fire text. Jake's reply was swift and concerned, promising to be there with Lady Rainicorn in a flash. Next, a hesitant message was sent to Marceline's device, carefully worded, suggesting an urgent problem that might concern her "family." Finn was still unsure what that meant, but PB's urgency had been contagious.
As the sounds of Jake and Lady Rainicorn approaching the Tree Fort could be heard in the distance, Princess Bubblegum activated a salvaged sensor, its weak beep indicating a faint, erratic energy signature flickering somewhere towards the outskirts of the kingdom. Cassian was out there, a ghost of destructive energy, lost and dangerous.
The hunt for the unstable demon had begun.