Lucien Dolo, a diamond dealer candidate for the Municipal Council of Antwerp, is the subject of a press campaign insinuating that he would be responsible for the mysterious disappearance of his brother Frédéric-Sébastien, known as Freddy during an expedition to the Congo, in which Lucien had participated. Freddy's bad reputation and the hatred existing between the two brothers gives substance to this suspicion. In order to lift the charges against her husband, Isabelle asks Inspector Wens to investigate.