The second rule for using a dash is for a complete sentence that is dropped into the middle of another complete sentence.
...I am looking at the article that -- it is the first one on the page -- was written about the new tax laws.
When this happens, there is no cap for the complete sentence after the first dash. If the sentence inside is making a statement, there is no punctuation for it; if it is asking a question, there is an interrog.
...Please turn to page 5 -- it is entitled "The Auditing Process" -- in the blue booklet.
...Please turn to page 5 -- have you read this? -- in the blue booklet.
...Have you seen Dr. Johnson -- he is the one that treated you for the foot problem -- who works at the UCLA clinic?
...Have you seen Dr. Johnson -- did he treat you for the foot problem? -- who works at the UCLA clinic?
Notice that the terminal punctuation for the sentence is for the sentence that has been interrupted.
Happy punctuating!
Margie