This article considers the role of the sister figure in Bruno Jasieński's early verse. His poems as well as various facts from his biography leave little doubt that this highly significant role was filled by Irena Zysman, his sister. The key to the dialectic of her presence/absence in the poet's life and work is to be found in the concept of melancholy. Although Jasieński would hardly be credited with that kind of sensibility, the relationship with his sister does show that melancholy was part of his psychological makeup. Moreover, by bringing in psychoanalytical analysis, the article shows how his melancholy morphed into mania, a transformation which in a way fuelled his political engagement.