The Great Impersonation by E. Phillips Oppenheim

There were times during their rapid journey when Seaman, studying his companion, became thoughtful. Dominey seemed, indeed, to have passed beyond the boundaries of any ordinary reserve, to have become like a man immeshed in the toils of a past so absorbing that he moved as though in a dream, speaking only when necessary and comporting himself generally like one to whom all externals have lost significance. As they embarked upon the final stage of their travels, Seaman leaned forward in his seat in the sombrely upholstered, overheated compartment.

"Your home-coming seems to depress you, Von Ragastein," he said.