Thanks so much for clearing this up! I received the DVD set as a present earlier this week, and have watched the first three discs (3 episodes apiece) each night. At the end of Episode 11, which I thought was the end of the 4th disc, you can imagine how I was left feeling exceedingly disappointed & let down to think that the whole series led up to just that. I even "surfed around" the disc, visiting the main menu, etc. - still couldn't find it and gave up. But apparently I missed the right button!
I have been mystified all day, since various websites describe "13 episodes!" Should have come here first... :)
The DVD cover really should be redesigned somehow to indicate that there are four episodes in the last disc.
I am going to pop disc 4 back in and sip a glass of champagne as I enjoy the final two installments.
Again, much appreciated!