How does Jack finally get Gunnar's letter to Emmaline?

First Jack tries to mail the letter, but it comes back "Return to Sender." Jack has to write a paper on a famous poet, so he chooses Hopkins because of his experiences with Gunnar. At the library, Miss B shares a copy of her own book by Hopkins. When Jack sees the inscription inside, he realizes that she is Emmaline, and he gives her the letter.