This article focuses on Ferdinand Hodler's cycle depicting his partner Valentine Godé-Darel during the cancer disease that killed her (1914- 1915). If Hodler seems to refer to the post-mortem portrait tradition, in which there are some examples of realistic representation of physical decay, his cycle stands out because of the incessant repetition of Valentine's sick face through which he sharply represents the metamorphosis of the woman. We find similar examples only starting from 1980's in the field of photography. The sense of Valentine's cycle is rooted not only in an aesthetic dimension but also in an ethic gesture. In fact, the act of representing with insistence and truth a beloved person dying could be interpreted - and some scholars did - as an expression of the supremacy of aesthetic interests over the compassion that such an experience should stimulate. Yet, the analysis of Hodler's carnets on Valentine's disease rather reveals Hodler's will to become the witness of Valentine's pains by means of his art.