This is a great premise for exploring human longing, connection, and isolation, especially from a Queer perspective. The couriers, conscripted into their jobs, mistrusted by society, and living on the fringes, have their own troubles and mysteries to deal with over the course of the story. But The Night Post occasionally has them read the letters they carry, which are often insights into the troubles, struggles, and desires of everyone. There is a mystery to solve, but there is also human emotion and love.