The characters involved in the murder in each of the compositions are identical. Marie-Thérèse is the victim and Olga is her assailant.
In "The Unknown Masterpiece" the murderous attack is related in a cryptic fashion. Marie-Thérèse is being mortally wounded by the 'U' shaped darts stabbing into her neck and shoulder. The darts symbolize and wounding represent pairs of bull's horns and the goring of the horse in a bullfight.
The darts emanate from a cache of similar shaped lines which appear hidden behind Olga's back. A similar assault upon Marie-Thérèse can be found in Picasso's poems of 1935, in which she is "reduced to the miserable state of the wounded horse in the bullfight" and "subjected to obscene insults and injury."*
The carving knife in both the earlier drawings from 1934 has also been cryptically incorporated into "The Unknown Masterpiece," where it reappears in the form of Olga's nose, knife-like and pointed in the direction of Marie-Thérèse.
* From a study of Picasso's poems by Jose Barrio Garay, quoted in Hershel.B Chipp's, Picasso's "Guernica", History, Transformations, Meanings. Thames and Hudson, 1989.
For additional information please read the following sections:
1934, The Biographical Background
The Bullfight Theme