Milverton blackmails Mary, exploiting her dalliance in antigovernment activities as a student. Sherlock decides to sneak into Milverton's estate to steal his evidence, but even that act was anticipated. Sherlock finds that he is not the only trespasser.
This matter was one of mine
and Mary's to begin with!
¡Además, este asunto nos
concierne en principio a Mary y a mí!
À la base, cela concerne Mary et moi !
Este assunto é meu e da Mary!
И вообще, это наша с Мэри проблема!