They are invisible is a Science Fiction (Space fiction) narrative about an investigation for the possibility of the existence of extra-terrestrial civilizations and their agenda to usurp our planet (the Earth) as their 'second Earth'. It mainly plotted from the realistic events and scientific phenomena. The novel actually talks not about extra-terrestrial life, but extra-terrestrial intelligence. The mystery of this novel lies in the description of Crop circle images, mysterious signals from the space received, Busegi chambers and the Area 51. The novel interlinks the Covid-19 pandemic to the extra-terrestrial civilization. The Greek myths and Stephan Hawking's concept of alien life are also mentioned in the story.