He's the Doctor After All
Two sets of eyes followed the Doctor around the room as he bounded about the console, pressing buttons, pulling levers, and exclaiming about "a planet covered in roses!" Jack leaned against the railing, quiet for a change and without the normal spark that shone from behind his eyes. The Doctor was oblivious to the difference in Jack. As he prattled on, practically skipping with excitement, he only had eyes for Rose.
"They grow a rose in a color you don't have on earth. It's a velvety purplish-blue that glows like moonlight, and would look absolutely fantastic tucked into your hair," he said. Rose blushed and Jack looked down as the Doctor reached up a hand to tuck a piece of Rose's hair behind her ear. He gave her a crooked smile, his eyes warm and tender, and then turned back to the console.
Rose looked up, saw the expression on Jack's face, and understood. Rose caught Jack's eye and motioned towards the hallway with her head. Jack nodded in agreement.
"Doctor," Rose began, "I'd better change. You said it would be warmer there."
"I'd better change as well," Jack echoed, still looking towards his feet.
"Yes, of course," the Doctor replied, distracted by flashing lights on the Tardis console.
Rose walked into the hallway, looking back towards Jack as she went. Jack followed her, watching as the Doctor ran a hand through his hair and fiddled with dials. They barely made it out of the Doctor's earshot before Rose turned to Jack and said, "I know, Jack, I know," and threw her arms around him. He gave into her embrace and buried his head into shoulder.
"I'm sorry, Rose, I can't help myself. But I know I'll never have him for myself. He's yours not mine."
Rose pulled him closer and whispered "I don't know, Jack. I don't think anyone can really have him. He's the Doctor after all."
They broke apart, and he gave her a wan smile of thanks. Rose wiped away the tear on Jack's cheek, and took his hand. The Tardis hummed comfortingly as Rose led Jack back into the console room.