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.
That won't be necessary.
Das ist nicht notwendig.
Eso no será necesario.
Non, pas la peine.
Isso não será necessário.
Можешь не напрягаться.