Finchley, 1942, two girls- or perhaps two women who appear to be girls- are throwing snowballs at each other in a park.
Ooh! That looks like fun! And it's hard to not know the rules of a snowball fight.
Here is someone new, looking about ten or eleven, with winter-appropriate clothes (except for no hood, letting that improbably full and shiny hair flow). With a snowball. "Hark! A new challenger approaches!"
"Lucy, Peter, Edmund and I grew up in another world where time passes more quickly than here, then got sent back to this one and put back into childrens' bodies. We got back there later, but by then most of the friends we'd had there were long dead.
I'm Susan and this is my sister Lucy. It's nice to meet you."
She sighs and starts walking towards her house
"Germany is already fighting a lot of people, 'though. They're at war against this country, and a lot of others. I don't think they'd be able to do much about it if we did rescue people from them.
Would it help if I told you more about what's going on? It sounds as though you're new to this world."
"My world was really cool! There were witches and wizards and summoners and void things and werewolves and sand magic people and angels and animals that could talk and vampires and people who were rocks and pirates and these cute fluffy people with a spaceship and hextech and spirits and ghosts and meditation magic and a whole bunch of cool heroes all over the place! Too bad it was so magic, that the whole place exploded when there was a big war. I... I ran away. I kinda miss it."
"I think I do. I've only known two worlds, but I've spend half my life in each of them and I miss the Narnia I knew, and all the people I knew there, now that its a thousand years past and I can't go back. I'm trying to move on, but it's difficult."
She pauses in thought. And then Lucy and two children come outdoors.
"Be right back!"
She steps through a portal that gives a glimpse of - multicolored clouds - and disappears.
Thirty seconds later, she steps back into the room from a paddy field. "I found some China farmers. There's actually a war here too I think... But not near this place."
The peasants in the background are abandoning their farms and scattering.