This is set after season 1, episode 4 :)
A Lost Hope
Optimus leaned his muscular protoform against the door frame to the med-bay. His spark melted when he saw her. Arcee.
She was recharging on one of the med berths, after having an operation. Megatron shot her with dark energon which left her on the edge off-lining.
Optimus winced at the thought. He couldn't bear life without her...
He slowly walked towards the berth, not taking an optics off her. Ratchet said that she was stable but still in critical condition. Optimus looked down at the femme in front of him. She was so innocent. So weak..
He checked for any life signals around, Cybertronian and Human. Bumblebee and Bulkhead was dropping the kids off home and Ratchet was in his quarters filling in medical data-pads. Good.
Optimus lowered down on one knee and placed a grey servo on the berth. Arcee's usually bright blue optics, was a dull navy colour meaning her optics were off-lined. Optimus could still remember the first day he laid optics on her...
...
Optimus looked around for Ironhide. That red mech always got himself into mischief.
Crowds of mechs and femmes all barged their way past Optimus, in the opposite direction, bumping into his broad shoulders.
Suddenly a blur of blue flashed before his optics. Next thing he knew, he was on his back with a femme on top of him. As the femme lifted up her helm, the Prime's faceplates started to heat up. When their optics finally met, she immediately pushed herself up from his chassis.
"Oh Primus, I'm so sorry!" she exclaimed.
"Urm.. I's f-fine." Optimus couldn't help but stumble over his words. The femme was beautiful. His joints suddenly felt weak.
"My names Arcee." she said with a smile.
"O-optimus..." he replied. Silence fell upon the two bots.
"Well I'll see you around then."
O-ok."
Arcee walked away leaving Optimus love struck.
…
Optimus took shaky intakes as his optics wandered, looking at her helpless frame. He raised a shaky servo and gently touched her pede. Optimus wandered his servo up her curved les, up her waist and up to her face where he caressed at her cheek plates with his thumb. Optimus knew he shouldn't be doing this but his inner feelings took over. He loved her more than anything but as a Prime, he's not allowed to put one's life before anyone else's so his love had been hidden for all these centuries.
His spark throbbed, wanting to reach her's. It was the pain he would always feel when she was near him.
Optimus lowered his helm until their fore helms were touching. He took shaky intakes before whispering into her audio receivers.
"Remember that I will always love you even if you will never feel the same way about me. Whatever you do, don't.. don't scare me again. I don't know what I will do without you. Your the one who keeps my spark pulsing. The one I love.."
Optimus off-lined his optics as a tear ran down his cheek plates. He was grateful that the others were away. They'd never seen Optimus like this. And never will. Optimus was thankful for his battle mask. Without it his emotions would become too clear.
He on-lined his optics to look at Arcee's beautiful face. After a while, his optics gazed to her lips. Oh how he longed to kiss those lips. Then, without thinking, Optimus gently pressed his lips on hers. He off-lined his optics to sink into the beautiful moment. Optimus groaned. He had always wanted to show his love to her. Optimus pushed a lightly harder on her lips. He could've sworn she kissed back...
As he pulled away another tear escaped his optics, sliding down his cheek plates. Optimus look down at Arcee's emotionless face, devastated that she wasn't awake to see him. He bowed his helm.
"D-don't leave me.. please.."
Optimus lifted his servo's to his faceplates trying to hide himself from the world. He took long, shaky intakes before getting up on his pedes. He turned for the door then stopped. Optimus looked at Arcee one more time before heading for his quarters, helm held low..
The End