A/N: Italics are from Captain America: The First Avenger (2011). Just playing in the sandbox of these fandoms. It's happier here. First written in 2020, edited in 2021.
A Prologue of Sorts…
She stayed invisible, scouting the area and trying to figure out how in the name of Morgana she had landed in an Officer's Club during World War II. Was it really 1943? And why did the air feel so different from home? Wandering through the smoky bar, her eyes found the only woman and followed her. It was relatively easy feat to accomplish, seeing as the woman had walking into the bar in a red dress. Definitely wasn't going for subtlety there. She waited to try to get a sense of what was happening. The conversation wasn't particularly enlightening, but Hermione knew for sure something was very wrong with her situation.
"I'm invisible," the darker haired soldier stated to his companion as the woman sauntered off. "I'm- I'm turning into you. This, what a horrible dream." His companion gave meaningless platitudes before offering some non-existent hope.
"Maybe she's got a friend." But to Hermione, she couldn't understand why anyone would want the lighter haired man over the dark haired one. Passive use of legilimency offered Hermione a better look into the situation. She was fucked. A Hydra didn't exist outside Greek antiquity and Super Soldier Serum? What in the world had she gotten herself in to?!
As going home wasn't going to be as easy as apparating, finding a quick exit that didn't bring attention to the random invisible woman was high on her priority list. Hermione found an unoccupied loo and shimmied out the window (something she hoped she would never have to do again, men's loos were disgusting no matter the era). Quickly finding a deserted alley she could ward and hide in, Hermione did her best to stop the shaking of her hands. It wouldn't do to mess the spell up and call further attention to herself in this strange new world. But instead of easily casting the spell three times for full coverage, Hermione had to cast the spell seven times, each time taking more effort to cover less space. 'It appears that magic here was not as abundant in this place', she thought to herself. She would have to use magic sparingly.
In another place and another time, Harry Potter and his team of Aurors wandered around a decimated flat. Three Death Eaters that they had been hunting were found dead or near death and it looked as if a small explosion had taken place inside a pentagram. Harry couldn't be sure as the blast radius seemed to have destroyed some of the chalk lines and he had never taken Ancient Runes, but it had all the markings of a dark ritual. Time to call in the Unspeakables. Sighing, Harry wondered out loud, "Where are you Hermione?"