Basil by Wilkie Collins (1824 - 1889)

Basil, son of a father who values the family pedigree and who would not let him marry below his station, falls in love at first sight with a girl he sees on a bus. He stalks her and discovers she is Margaret Sherwin, only daughter of a linen draper. He stalks her and persuades her father to let him marry her secretly. He agrees on the condition, that, as his daughter is only seventeen, they live apart for the first year. At first the secret works, but then the mysterious Mannion, whose emotions cannot be read in his face, returns from abroad. On the last night of the year Basil follows Margaret and Mannion and discovers them in flagrante delicto. (Wikipedia)