The novel is set in Argentina at the outset of commercial aviation. Rivière is the station chief of an airline that is the first to pioneer night flights, disciplining his employees to focus all they do on ensuring that the mail gets through punctually each night. The novel's episodic structure is built about his work at the Buenos Aires office and the final hours of the pilot Fabien on the Patagonia run. Fabien's plane is caught in a cyclone, runs out of fuel and loses radio contact, while Rivière tries all he can to locate the aircraft. At stake is the future of the night mail-run to Europe. Once the two other flights from Chile and Paraguay get through, Rivière has to allow the trans-Atlantic flight to Paris to depart without the missing mail, resigning himself to Fabien's loss.