Black Butterfly

S3 E3: The charred body of a medium is found in the gutted remains of her office after a fire. When another two murders take place in the same manner, it becomes clear to the Gotland police that they have a serial killer on their hands - but without having the slightest idea what the victims had in common, or who the next one might be. Maria Wern is forced to lead an investigation where neither the motive nor the victims seem to be connected — at the same time that her colleague Arvidsson’s loyalty is forcibly put to the test.