Weapons of Mystery by Joseph Hocking

Justin Blake receives an invitation from his old school-fellow Tom Temple to join him and his family for the Christmas holidays in Yorkshire. Having no other plans, he decides to go. Though he is normally much the opposite of what would be called a lady's man, he falls instantly in love with Miss Forrest, one of the guests, who had already shared his train compartment on the way. When he meets the mysterious Herod Voltaire and finds that he must protect the girl from him and his weapons of mystery, the adventure begins.