Every Tree That Is Pleasant, by spitandvinegar

“It hasn’t been two weeks, where they are.” 

Natasha felt something cold settle in her gut. “How long?” 

Wanda said, “I’m sorry, I’m so sorry.” Then she said, “Twenty years. They’ve been alone in the jungle for more than twenty years.”

Adult, AU, AO3 users-only. This fic is like nothing I’ve read before. Steve and Bucky get stranded in another dimension without their memories – and when they return, their friends have to cope with two people who’ve somehow merged into one. Absolutely fascinating!