So when character A timeslips, he/she first meets character B, after which both timeslip simultaneously?
There must be a simpler basic concept...
Yes, that is confusing. But let's face it, multiple contributors with varying expertise areas makes for some degree of intricacy! I'm just trying to come up with something here.
So how about 20-year-old Ella meets Jon while backpacking with separate groups of friends in New Zealand. (I am picturing Middle-Earth here ). He is 30-something, following his father's footsteps in the diplomatic corps of (any country, but he can speak her language). she is a Navy brat who has lived all over the world. Their diverse backgrounds, which have always made them seem like a fish out of water in normal company, strike a chord. (Please, lets not have them both be drop-dead gorgeous, okay?)
They talk for a while over the campfire and decide they will pair up to climb Mount ? on the following day.
A windstorm comes up in the process, and Ella sprains her ankle. Jon, annoyed that she has over-represented her climbing abilities, finds a nice cave, tucks her in for the duration and hikes down to get help.
Ella feels odd. She drifts off.
But when she wakes up, she is not in the cave. In fact, she is not in her old body, or the clothing she had on. And the weather is different. And she has an additional, completely new set of memories. But she has one thing with her that she did have in the cave, her only link to sanity...
Now how Jon gets there, I haven't worked out, but it should have something to do with Ella. Maybe the something significant that came along is his. (okay, that's a fantasy element, but hey, you gotta have a plot device when you need it). How about an old-fashioned-looking compass? That could prove very useful wherever she lands. Or a ring, or other bit of jewelry.
And the thing is what yanks Jon to the same place, within a radius of ? miles, and arriving within the next week.
That's the best I can come up with in ten minutes. I'm sure the rest of you have better ideas.