While drinking at their club, a group of gentlemen take part in a speculative conversation about other life forms. Discussing notions of time and space in relation to the existence of extinct civilisations, Dr Ptolemy Posa informs his companions of the Duodims who inhabited a two-dimensional 'surface world': '"The Duodims," said Posa, "are like the Dodo - they are extinct; but they existed, I know they existed. They inhabited Plateterre, which has followed Atlantis and Lemuria into nothingness."'