A/N: This story will be a thoughtful exploration of why Susan forgets Narnia. I speculate that there's a bit of magic involved— as well as painful memories, estrangement, and unconditional love. I'll introduce a lot of new characters, both English and otherworldly. This will begin at the train station after the events of Prince Caspian and span several years. I'll include a lot of exploration related to Uncle Andrew, Mrs. Lefay, and Digory.
In the dim light of the railway station stood a girl, her hands clenched in the pockets of her jacket. Her face was pale, her posture stiff, and her hair unkempt. Catching a glance in a grimy window, she began furiously straightening the stray locks. A group of gangly youths passed, shooting sly glances at her. But she abruptly laid down her hands and stared dully at an approaching train. Her freckled nose was raised a little, her mouth pressed into a firm line.
On a bench behind her sat two boys, one sleeping while the other stared sharply at nothing, as if on guard. They were dressed in drab uniforms with stiff collers. A smaller girl was wandering about, looking down the train track and perusing stray pamphlets. She looked bored, and soon returned to the three others. As the train heaved to a stop, she approached the older girl, who was obviously her sister. They also wore uniforms, though bearing a different insignia.
"What did Aslan say you, Susan?" cried the younger girl without introduction. "I know I couldn't bear it, never coming back to—"
"Quiet, Lucy! Do you see where we are?" Susan's eyes narrowed, and her eyes flicked to the group of boys, standing a few yards away.
"You are a wet blanket," said Lucy. "And all because of those silly schoolboys! I thought you were making eyes at Caspian, but of course that didn't last."
"It couldn't," Susan muttered. He was so hurt— so strangely hurt. I felt strange too, but I could hardly understand it… she pushed her thoughts away, only to be confronted by a lump in her coat pocket. That bundle was her last bit of hope.
"What? What did you say, Susan? Wake up! You like Caspian, don't you?"
"Nonsense, Lucy. I'm too young to make a fool of myself like that. And I am resigned to never visiting— playing those games— again. I knew the end of it was coming." This was not strictly true, although she had been filled with vague foreboding during the battle. But that was only natural. Could she really call it a premonition? Guilty, she added, "At least, I knew we couldn't be children forever."
"It's not a game, Susan!" cried Lucy. "And we were grown-up there too, the last time. If you were grown-up would you marry Caspian?"
"Most likely not. I was grown-up a thousand years before he was even born." This statement earned her a curious look from a passerby. Susan bit her tongue. Act like a queen, Susan— gentle, quiet, dignified…
"I wonder if I'll go back," Lucy mused, more to herself than to Susan. She seemed to have forgetten that she was not alone, and that she was speaking aloud. "I do hope I shall."
"Don't think of it now. Live your life, Lucy. No use dwelling on Narnia when you're not there."
"But Narnia is so much better," Lucy whined. She was only nine or ten. She still claimed the right to be a baby now and then. Susan sighed, annoyed.
"I imagine Peter Pan felt that way about Neverland. As if it means anything." Susan resented her own voice even as she said the words. What was she becoming— boring, bossy, even indifferent? She didn't recognize this new Susan.
"I'd live in Narnia forever if Aslan would let me. Say, Susan, what if I'd landed on that island by mistake? With all the Telmarines? I suppose I'd like that."
"Aslan doesn't make mistakes like that. And think what they'd do to you."
"He said they'd do terrible things to Reepicheep, not me," said Lucy. "I could marry the Telmarine leader and live in a grass hut. It would be jolly. You know I love tropical fruit, and I could climb all the trees I wanted, and tame goats—"
"And be wet and cold, and sick half the time? And lose your complexion in the sun. You're lucky, Lu… you don't have half the freckles I do."
"I like your freckles. They make you look less like a dignified bore and more like someone fun. Even if you aren't."
"Thank you," replied Susan, accepting the dubious compliment with queenly grace.
"And you don't have to worry about being babyish, because Aslan doesn't want you in Narnia anyway. So enjoy being grownup."
Susan winced. But Aslan said he would take care of me... to not be scared if he fetched me again. Just not to Narnia. Could it be Narnia? Can I be sure? Susan doubted everything. For all his goodness, Aslan was not tame, and he often spoke in riddles.
"Susan? I'm going to go talk to those boys if you're so boring. Goodbye."
And Lucy turned and walked deliberately towards the group of hooligans. Susan's silent gasp and frown were only ignored. It was time to take action, Susan decided. But her indecisiveness had lasted long enough, and by now the circle of boys had parted. Lucy stood before them, looking small and vulnerable. Susan hesitated. Then she gritted her teeth and took a step towards her little sister.