In which young Rob returns home from his remarkable adventures to find his family relieved and curious, while his mysterious visitor, the Demon, arrives once more with reproaches and a stern demand that Rob share his wondrous inventions only with the cultured minds of the world. The Demon’s ire gradually softens as he exchanges Rob’s damaged machine for a sturdier one and promises further magnificent gifts, on condition of a solemn promise to forsake uncivilised realms.