This was a request from RisingGundam2006. Set during 'Sick Mind'.

Optimus lay on a berth in the med-bay, groaning in pain as he watched Ratchet scan over Optimus's optic. Arcee sat by his side holding his hand tentedly in her own, whilst the other rested over his abdomen. She occasionally wiped away a stray tear that fell from her optics.
"Cybonic Plague." Arcee dropped her head down onto Optimus's hand, "It's only infectious if contact is made with the infected energon." Optimus, to the best of his ability, squeezed Arcee's hand . She looked up at him, both optics swimming in tears. Seeing Arcee's pain broke Optimus's spark, this wasn't meant to happen.
"What was a plague doing in an Autobot spaceship?" Miko asked sadly from the upper railings above where the bots stood. Trying her best to keep herself in check, Arcee wiped away the tears and took a deep breath, "It's passengers were infected. The virus wiped out millions on Cybertron during the Great War." She felt her tears come flooding back as she thought of all those she had lost due to the plague. She couldn't lose Optimus to it aswell, she couldn't lose Optimus ever. She needed him to much, he kept her going, kept her strong.

Standing, Arcee pulled her hand away from Optimus's own. She unsteadily walked around to his face, never taking her optics away from his eye. It was dark and swollen, cracks ran down the sides of his optics and the light of his optic was dimmed and had a tinge of purple to it.

"Cybonic plague was engineered in the Decepticon Biological-warfare programme. By Megatron himself." Ratchet spoke gravely. Arcee reached her hand out, gently stroking the side of Optimus's face. She trailed her fingers upwards, towards his optic, when Optimus's hand came up to grasp her wrist and pull her hand away.

"Don't touch... my wound. I don't... want you... to get sick." He weakly pushed out his words as he held her hand over his spark.
"You have a cure don't you?" Raf spoke up from the railings.
"No... cure." Optimus's voice was raspy and low.

"Optimus please. Save your strength." Ratchet pleaded with his commander. Arcee kissed Optimus's healthy optic whilst his grip tightened on her hand as pain coursed through him.
"Would Megatron create a disease without having a cure? I mean, what if he caught it by accident?" Jack made a good point, and they all knew it. If Optimus was going to be saved, Megatron was the only one who could do it. But that was out of the question.

"It's not like we can ask Megatron, Jack. He's pushing up lug nuts."

"But... we might be able to access the Decepticon data-base. For the moment, we still have a fix on their warships location." The team knew what Ratchet wanted them to do. Sneak aboard the Nemesis and save Optimus.
"Bumblebee, come with." Arcee made to pull away from Optimus, but he tightened his grip on her.
"Don't... go. Please" He rasped, his optics locked on hers, all his emotions flooding to her.
"I can't stand here and watch you die. I'll come back." She whispered to him. She kissed his forehead, cheeks and lips as she felt his hold slacken but not completely let go, "I love you." She whispered into his audio receptor. She removed herself from his reach before he changed his mind. She and Bumblebee prepared themself for the mission as Bulkhead readied the bridge. Arcee could hear Optimus's pained groans from by the bridge as Ratchet turned his head to face her and Bee.
"Arcee. Quickly." Nodding, she and Bumblebee took off into the green vortex.

The two Autobots broke into the Decepticon war-ship guns at the ready. After accessing their surroundings, Arcee took point.
"Lets start with the lab." The noise of a door opening forced the two into hiding. Arcee jumped up into the rafters, while Bumblebee ducked behind a wall. Knockout was oblivious to Arcee over his head as he walked past them. "Come on. The labs in here." The door re-opened for the Bots. "You keep watch, I'll search the data-base." Arcee instructed as she began to comb through each file on the data-base. Bumblebee stood watch by the door before surveying the lab. "I'm in the network." Arcee open commed to base. Slamming her fist on the keyboard, she huffed angrily. "If it's here, I don't see it."
'Arce you certain, Arcee?'
"I've searched every file. Nothing."
'Well search again! Clearly you missed something!' Ratchet angry voice blazed through the comm. In her peripheral vision, she could see Bumblebee peering through the seperate labratory room. She took no notice. "I scanned the entire data-base!"
'Cee... you should come and see this...' For now she ignored Bumblebee, Ratchet wasn't taking no for an answer.
'Did you a redundant quantum algorithm?'

Arcee rolled her eyes, "Don't tell me how to research! You think your the only one who cares about Optimus?" Her question didn't need an answer. Ratchet, and everyone else, knew the extent of Arcee and Optimus's feelings for each other.

'Seriously Cee. You need to see this!'
"What is it!" Arcee reluctantly moved away from the monitor. Since he lost his voice-box, Bumblebee's eyes were the main give away for his emotions. As she approached him, she could see fear and confusion in his eyes.
'What is it? Whats going on?'
The door opened as Arcee gasped in surprise, "It's Megatron! He's alive!" Since the comm-link was open, everyone in the base could hear her, and she could hear all of them. She could hear Miko's shocked gasp and Jack's shout of 'What!'. Arcee and Bumblebee cautiously walked into the room, guns pointed at Megatron's still body. 'That's not possible!'
"Well I'm staring right at him. Good news is, Megatron isn't exactly staring back!" Aiming her gun at Megatron's head, Arcee prepared to take the kill shot. End him once and for all. Her spark ached when she heard Optimus weakly groan.
"He's critical. Hooked up to life-support. Time to finish this once and for all." Her gun loaded up and she could see Bumblebee doing the same from the other side of the berth.

'WAIT! DON'T!' Ratchet shouted to her.
"Give me one good reason! Fast!"

'Megatron may be Optimus's only hope of survival." Arcee's aim faltered and she decelerated her gun.

"What are you talking about?" Bumblebee watched her from his position, all the while keeping a guard on the door.
'Does he display brain-wave activity?' Arcee moved over towards the monitors. The tubes attached to Megatron all linked to this machine.

"Spiking hard," Bumblebee came up behind her to see for himself, "His sick minds still at work." She seethed. Shock once again coursed through her as Ratchet announced, 'Perfect!' 'If a cure exists, Megatron may be the only one who knows it. You must enter his brain, and find it.' Arcee and Bumblebee locked optics in surprise. How would they be able to search Megatron's mind, what with his being borderline deceased before them.

"Enter Megatron's brain? Ratchet are you out of your fragging mind?"

'The Decepticon labratory should contain all the equipment you need for a Cortical Psychic patch.'
"No way!" Arcee knew all to well about the patch, having experienced it at he hands of Shockwave before coming to Earth. "Have you ever even performed the procedure?"
'No.' It definitely wasn't the answer that she wanted, ' But I have thoroughly studied the theoretical literature. Invented by Decepticons; Outlawed by Autobots.'
"Can't we just haul Megatron though the Ground-bridge? Buy us some time to figure this out?" Arcee's audio processor ached at the volume Ratchet spoke with.

' Time is one thing that Optimus does not have! One of you must try this! I will not allow Optimus to pass, knowing that Megatron will out-live him!'

Letting out a deep sigh, Arcee looked at Megatron. The mighty warlord looked weak in his current state. Her mind drifted to Optimus, and ow weak he looked on that berth. Wounded and tired. She couldn't let him die like that. "Ratchet I would lay down my life for Optimus. If a mind-body split is the only way, I'll do it."
'Arcee... No! I can't... let you... do this. Please.'

"Optimus, if I don't you'll die. I can't lose you either. I can do this." She tried her best to reassure him, but she herself was worried. She barely survived the last mind-body split that she'd endured. It was a dangerous procedure. But Optimus was worth it.
'Arcee are you sure?' Jack spoke to his guardian in an apprehensive tone. He didn't know the full consequence of the split, but he was still worried about the idea of it. "I will be fine."
'Cee is one of the best scout's Cybertron had. She can do this Jack.'
Bulkheads words were aimed at Jack, but were also a reassurance to Optimus, who was just as worried about his femme.

'The equipment you need should be in the lab. You will need a...'

"I know what we need Ratch. Not my first encounter with the split." Arcee pulled a large wire out of a hidden cupboard and attached it to the back of Megatron's head. She jumped into a hidden dip in the floor and calmed herself, while Bee hid the wire from plain sight.
"Ratchet, we're ready." She informed as Bumblebee joined her. Arcee handed Bee the end of the tube as she dipped her head forward, 'Initiate Cortical Psychic Patch.' Ratchet instructed. Bumblebee gently pushed the end of the tube into Arcee's head, twisting it slightly into position. She tensed up and her optics flickered as the patch activated. Gently, Bumblebee took hold of Arcee's shoulders and held her against him. He rested her in between his legs, one of his guns activated as a precaution while the other held the femme close to him.

For her part, Arcee's world turned black and specks of light came rushing into her vision, as if she'd rubbed her optics to hard. She relaxed against Bee's chest. Rainbow colours shot at her from her optics as her vision became clearer. the lights moved faster and she came to her senses, not in Bee's arms. On Cybertron.