Tasio Ortiz de Zarate, the brilliant archaeologist found guilty of the bizarre murders that terrorised the peaceful city of Vitoria twenty years ago, is about to leave prison on license when the crimes begin afresh: the naked bodies of a twenty-year-old couple are found in the symbolic building of Vitoria's Old Cathedral, killed by bee stings to the throat. Not long afterwards, another twenty-five-year-old couple are killed in the Casa del Cordón, a well known medieval building. Young inspector Unai López de Ayala —alias Kraken—, a criminal profiling expert, is obsessed with preventing the crimes before they take place and a recent personal tragedy prevents him from treating the case as just another job. His unorthodox methods annoy his boss Alba, the deputy superintendent with whom he has an ambiguous relationship, marked by the crimes... Time is against him.