After another dreary term away at school, Grace is desperate to see her mum and brother again. Excited to spend Christmas with them, she arrives in Bath full of expectation and happiness. But the family's time together is suddenly interrupted when a shocking murder at their hotel throws everything into chaos. And when Grace's mum disappears soon afterwards, Grace trusts nobody. With her mum missing and younger brother Billy in tow, Grace enlists the help of new friends Olive and Doug. Streetwise and clever, they help Grace and Billy come up with a plan to find out why Mum left the hotel and what happened to her. Full of twists and turns, the mystery takes the four friends on an adventure. And as they start to uncover the truth behind the murder, they wonder if anyone at the hotel is really who they say they are.