The Flames which consistes in three part and every part is connected with the end of the previous one. The short novel, has the form of a long letter written by one old university friend to another. The recipient of the letter, known only as "Thos" introduces the strange document, from a friend known only as "Cass" (another nickname; short for "Cassandra"). 

Cass`s letter, which forms the bulk of the novel, describes his contact with a bizarre form of alien species. Whilst holidaying in the Lake District, Cass is inexplicably drawn to a lump of rock, which he pockets and takes back with him to his room. There, he is driven to place the rock on the fire, and this action releases a bizarre form of alien life - a living flame, which has been trapped in the rock for millennia. The flame reveals itself to be one of an ancient alien race who originated in the photosphere of the sun. Solar catastrophe has distributed the ancient race throughout the planets of the solar system, and the flame-beings can only be woken by intense heat. The flame and Cass discourse at great length about typically "Stapledonian" topics - the life of the spirit, the role of the individual and the purpose and meaning of the universe.