The gripping new YA thriller from the author of FOUR GOOD LIARS, and the perfect read for fans of A GOOD GIRL’S GUIDE TO MURDER. "A tense and satisfying cosy murder mystery, with an added really fun STEM element in the form of graphs, charts and Venn diagrams to illustrate the investigation – I loved going through all the workings!" Ravena Guron, author of This Book Kills How do you catch a murderer without knowing who the victim is? Science-obsessed Grace’s fresh start with her dad in Devon is derailed when the smart speaker in their new house comes alive at midnight and says: I’m going to murder you. And after Grace begins to investigate, she uncovers four mysterious deaths – all supposedly accidents – that are linked to the device. But only Grace knows that one of those deaths was actually a murder – and now she must identify both the victim and the killer, using the methodology of a chemistry experiment … before she ends up dead herself. The gripping new YA thriller from the author of FOUR GOOD LIARS. "An immaculately plotted, clever book with a great ending!" Sue Wallman, author of Lying About Last Summer