The Petersburg dreamer is the type of man the narrator describes in the Second Night, speaking of himself in the third person: someone who lives in a corner of St. Petersburg, barely speaking to anyone, and spends his free hours in an invented life, more intense than the real one. The Russian word is мечтатель, dreamer: one who lives by reverie.
In the portrait, the dreamer lives in strange corners of the city, where another sun seems to shine, and "clings to his corner like a snail". At the end of the working day, he walks home without seeing the sunset, because the goddess Fantasy is already weaving a story for him; he eats supper without noticing and wakes only when the maid brings him his pipe. In reverie he is a crowned poet and a friend of Hoffmann, meets the heroines of Walter Scott and wants nothing, "because he is himself the artist of his life".
The portrait is made with irony and with shame. The narrator asks to go on in the third person because he is ashamed in the first, and tells of the visit of an acquaintance who finds him disturbed and leaves laughing. Then he drops the pose and admits the price: the best years lost and a fantasy that grows tired, to the point that he celebrates "the anniversary of what was once so dear and, in truth, never happened".
The type admits two readings. It may be seen as an illness, life traded for images, and the narrator himself calls reverie a poison. It may also be seen as a form of sensitivity, that of someone who feels everything with force and only lacks a place to put what he feels. Nastenka, on the Third Night, says that the dreamer described is not him, that he is getting better; the end of the book leaves the doubt open.