When concert violinist Milan begins to hear musical tapping sounds that seem to be coming from somewhere inside him, he thinks at first that he may be losing his mind. But a scan at the hospital reveals the alarming truth: since birth Milan's body has been harbouring his twin sister - a rare medical occurrence that will turn his world upside down (or inside out).

At the centre of a whirlwind of media hype, Milan embarks on the most intimate and unexpected relationship of his life. His new-found sibling Roma believes there are only 147 people in the world. She has never seen the moon, never tasted her favourite wine. And as Milan attempts to introduce her to the world outside, he discovers for himself just how strange it really is.