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.