Eduardo Plaar, a young doctor of English heritage, moves from Buenos Aires to a small port town near the border with Paraguay. He is summoned to the house of Britain's Honorary Consul, Charles Fortnum, to tend to his sickly wife, whom he engages in an affair, resulting in her falling pregnant with his child.
In the midst of this situation, a group of Plaar's childhood friends appear to inform him that his father, presumed dead, is still alive in a Paraguayan jail. They hatch a harebrained plan to kidnap the United States Ambassador and use him as bait to demand the release of all political prisoners being held in Paraguay.
Their plan falls apart when they accidentally kidnap Fortnum instead of the US Ambassador. Despite the best efforts of Plaar, the situation devolves into chaos and as the book reaches its conclusion, the kidnappers, Fortnum and Plaar find themselves surrounded by armed police.