'I have long believed that loving a boyband brings with it a wealth of transferable skills, but I'd never imagined solving a murder would be one of them...'

Harri and her best friends worship Half Light - an internationally famous boyband.

When frontman Frankie is arrested on suspicion of murdering his oldest friend Evan, Harri feels like her world's about to fall apart.

But quickly she realises that she - and all the other Half Light superfans out there - know and understand much more about these boys than any detective ever could.

Now she's rallying a fangirl army to prove Frankie's innocence - and to show the world that you should never underestimate a teenage girl with a passion...