The Silent Barrier - Louis Tracy

Charles K. Spencer is a well-to-do young American mining engineer. Drinking his water in a hotel in London one day, he overhears a conversation between two young women, one of whom is to go to Switzerland. He decides to play "fairy godfather" and send the other girl there as well, also to further her career as a writer for a scientific journal. However, the girl is shadowed on her journey by the mysterious Mr. Bower. Convinced that Bower is a rogue, Mr. Spencer decides to follow them to protect the girl... (Summary by Carolin)