Secret service officer Bastel Colvaro, a scion of one of the seven families with the highest blood, receives a letter from his father asking him to return home immediately. Troubles on the trip are not long in coming. An attempt is made on his life at the hotel, after which he miraculously survives. The attacker is killed, but his blood, unlike the colored blood of high families and the low gray blood of other people, is transparent. In addition, an attempt was made on the sovereign himself. But neither the goals nor the motives of the killers are clear. Bastel is given the powers of an investigator. Transparent or, otherwise, empty blood becomes the main mystery...