Synopsis

The investigation revealed a meticulous crime. The baumkuchen had been sliced with precision into eight equal portions, and a single piece was poisoned. As detectives questioned the suspects, the widow, Serika Wakamatsu, remained outside their purview; she had no connection to the dessert tray. However, in Nagano, the police uncovered a hidden clue. The killer had rearranged the bathroom tiles, using the optical illusion of crazy diamonds to conceal a dying message – one that appeared impossible