The clock struck midnight

A girl of around 14 has ran outside his window at exactly midnight every night for as long as he can remember. He is now 16 and when one night the running girl has vanished he knows he must set out to find her and what she has been doing all these years.

A small boy has looked out of his window at her every night since she died. She then hopes that the boy would save her when in most peril and capture her back from the depths of time before it's too late for her and her secret gets out.