You know, dear, my ideas of the trust between husband and wife: there should be no secret, no concealment.
– Bram Stoker
Dracula, Chapter 9. Jonathan tells Mina that marriages should not have any secrets. This could be said to foreshadow that he will later break that trust. He and the other vampire hunters stop talking to Mina about vampires and decide to keep her in the dark about the fight against Dracula, until he is destroyed. With disastrous consequences – she is bitten by Dracula!