As he stepped into the Great Link once again, he kept Kira's words tucked into the back of his mind. A small space he barricaded off and refused to let melt into the link with everything else. Not that there was anything like true hiding within the link, but he kept the hope wrapped around the words as his own. A reminder of his individuality, and his ties to the solid world.
Maybe afterwards he could go back.
Spreading the cure took less than an instant, even to a solid's perspective, but it was teaching them about the solid world that was the lengthier task. He always knew that, but he held hope that the link would speed the process up significantly. That perhaps 'long' for the changelings, would not be long for the solids. That there would be time.
He left Kira with the impression that it could never happen, but he didn't dare to raise her hopes. He couldn't bear the thought of her pining away, waiting for him, when there were no guarantees. Even with a guarantee, a long wait for him would still have been unacceptable. No. Kira must be happy in his absence, she must be able to get on with living her life fully. He couldn't bear to be the reason for her brilliant fire to die down a little.
So one day he stepped out of the Great Link and became Odo again. He sat for a while, watching the link ripple and sway and enjoying the sensation of fingers and toes again. It was almost, if not quite, as soothing to watch his people as it was to commune with them. But eventually he pushed himself to his feet and drew on all the knowledge the others had shared with him, slowly merging himself into the shape of the flying creature that Laas had been when he'd found Odo for the first time. It was curious, he considered, how different the sensation was to be attempting to copy a shape for the first time from memory. He'd never considered it possible to do accurately before he returned to the link, but now he knew how so he slowly stretched himself into the change, flicking a fin every now again to test their flight capabilities.
But once the change was complete there was nothing holding him back, and so he propelled himself into the atmosphere and through into space. Then it was on to the wormhole, and straight through to Deep Space Nine.
His heart was singing for Kira as he travelled. He wanted to see her new life, meet her children. Hold her close. Find out whether she had been happy without him, like he'd told to be, and reassure himself that he could find a place in her life without disrespecting that. He'd find a way, any way, as long as he could see her again.
When he reached the station, he quietly let himself in via nooks and crannies and air vents, until he was able to reform on the prominard. He introduced himself to nearest security officer in as non-threatening a manner as possible, not wishing to alarm anyone before he could make enquiries as to where Kira was living and working now. He amused himself by poking around the office and remarking on how similiar it still looked, after they asked him to wait and proceeded to whisper frantically among themselves.
Odo's hopes soared when Captain Sisko walked through the office doors, but then they sank just as quickly. Sisko looked exactly as when Odo had last seen him, as though he hadn't had much of a chance to age yet, which didn't make sense. He didn't recognise any other people stationed on the station, and their uniforms had all shown that Starfleet had passed the station over into Bajoran control.
"Odo," Sisko said quietly, but warmly, and held out his hands. "It is very good to see a familiar face."
"I know exactly what you mean, Captain," Odo replied, and hesitantly stepped forward to grasp Sisko's hands.
"Please, Odo, call me Ben. As you can see-" Benjamin laughed and waved a hand at his clothing, "I am no longer a Starfleet Captain. I am now simply the Emissary."
Odo stared at Sisko's robes for a long moment, before he could work himself up to the question, but even then his voice cracked at the end.
"How long have I been gone?"
Sisko looked at him sadly, and released one of Odo's hands to pull him into a one-armed hug.
"Please, Cap- Ben," Odo protested, and was released.
"We have both been gone a little over a thousand years, Odo. The Prophets only recently returned me, so that we could work together once again," Sisko said. Odo tried to turn away, overcome, but Sisko refused to release his hand; instead raising his other to Odo's shoulder. "I'm sorry, Odo, so very sorry."
Kira was gone, forever. They really had been done in by time, like he'd silently hoped they wouldn't be. He could find and meet her descendants as he had planned, but it had been so long that it wouldn't matter. They wouldn't have memories of her, couldn't ease the lose in his heart with remembrances. She had lived the rest of her life, and had died, without him, and he had missed every last second of it.