When they were born, Hannah and Jo were identical twins. Unfortunately, only one of them, Hannah, survives their first few days. But from the beginning. Jo is there for Hannah. She's always been there. As a baby, this gave Hannah a companion. As a kid, this gave her a friend (albeit one who was invisible to everyone else). But as a 12-yr-old, this doesn't give her a minute to herself. And Jo also seems to be able to manifest in strange ways.

When Jo crosses the line one time too many, Hannah tries to break free - and Jo doesn't like that. Now Hannah's lifetime sister has become her worst possible stalker. It used to be that Jo protected Hannah at any cost. But now? Jo's found that the weaker Hannah is, the stronger Jo grows. And Jo is starting to think it's her turn to live.