The threshold

Aletha is sketching a century old abandoned miner's shack when a little girl appears through a tiny rip in time and space. They only see each other for a second, and then the rip closes back. With Aletha's sketchbook still in 1900. The little girl Callie and the woman Aletha are tied together, rifts opening at random, enabling passing between the two times in the same town, a bloody troubled mining town in Callie's time and a tourist attraction in Aletha's. Aletha repeatedly gets trapped in the past, wanders a bit, then finds her way back.