we'll never be parted (harrystyles ff)

Someones life is torn apart when their fiance dies right in front of them.
Mysterious letters from a guy that wants them dead.
Every little thing leads up to the murder of someone in the couple of Emma and Harry.
They are given three months to stop the mysterious guy,track him down and arrest him.
This story is all about luck.
Blood will be spilt and anger will show and love for and between others will grow stronger.