Passenger From Scotland Yard (Esprios Classics): a Victorian detective novel

"The night mail for the Continent stood ready to glide out of the London terminus, the leave-taking friends assembled in small groups upon the platform before the carriage doors were reiterating last messages and once more exchanging promises to 'write, ' when a hard-featured, thick-set gentleman who had been peering out of a second-class window drew back with a slight exclamation of annoyance or disappointment, and sank into a corner seat. Hardly a moment had passed, when the rattle of the guard's key was again heard in the lock, and the door fell open to admit a fifth passenger. 'Just in time, sir! ' muttered the guard, banging the door after the new arrival and relocking it. He immediately signalled with his lamp, a whistle rang out sharply, and the night mail for the Continent started from London."