The Silent Passenger

A blackmailer is murdered by the husband of one of his victims, railway detective Henry Camberley (Donald Wolfit), but it is the innocent John Ryder (John Loder) who is suspected of the murder when Camberley puts the dead body into his trunk. After making the casual acquaintance of Ryder, amateur detective Lord Peter Wimsey (Peter Haddon) sets about proving his friend's innocence. All these events take place while on a train trip from London to the English Channel, with Ryder acting as "bait" to flush out the real killer and solve the murder.