From Rotterdam Gerhard Bern has received the terrible news that for no ostensible reason his brother has committed suicide The only clue seems to be his membership of a secret club To find an explanation Gerhard accompanied by a detective hurries to Rotterdam where he is given accommodation by Consul Verstraaten a friend of his father There he meets and falls in love with the Consuls daughter Ilse and shortly thereafter they become engaged In the meantime another mysterious suicide has been reported It appears that in both cases the men both members of the same club had taken out a life insurance policy and that a certain Mr van Gelderen leader of the club has collected the insurance money