SAME? DIFFERENT?

Stacey and Stephie are identical twins but their fate has separated them. Their lives have been this way for years and now they are used to it. It's neither their fault nor their parent's. They had no choice but their was one privilege that they possessed. They were legally allowed to switch places. And nobody ever recognised that there was two of them. But the maximum days that they could pretend to be the other was only three weeks in a raw. But they were never bothered by that condition until Stacey found a puzzle with some missing pieces which cost some lives. Will she be able to find the fitting pieces before returning to her own place?