It's night, and Dusk is flying; she needs to return this library book before bed, and she's left it until the last minute, trying to read as much as she can before she turns it back in, but now she really does need to give it back and go to sleep.
Suddenly there's a huge golden ring hovering in the air in front of her, filled with a weird rippling redness; she tries to stop, but that's hard, in midair, and there's not enough room to dodge, either.
She goes through, and she's in the air above an unfamiliar island.
The library isn't going to get its book back on time, looks like.