Number 70, Berlin by William Le Queux

Three weeks went past -- dark, breathless weeks in England's history.

Jack Sainsbury, keeping the knowledge to himself, spent many deep and thoughtful hours over his friend's tragic end. Several times he suggested to Mr Trustram that, in order to clear up the mystery, the sealed letter should be opened. But Trustram -- having given his word of honour to the dead man -- argued, and quite rightly, that there was no mystery regarding Jerrold's death. He had simply committed suicide.