On The Calloway you are what you carry. Kit has carried other people’s words her whole life — a message-runner, fast and forgettable, threading the performance-train’s corridors with sealed letters she is paid not to read. When the loops of three great trains converge for a once-in-a-lifetime crossing, her Conductor hands her a simple, well-paid run across the gangway. It goes wrong in ways that are not accidents — and as the trains pull apart for years, Kit finds herself stranded on the wrong one.