Question about Beethoven?

What mode or scale did Beethoven use in his song Midnight Sonata Movement 3 in 5:40-5:44 (you can just skip to 5:40) in this video: http://www.youtube.com/watch?v=oqSulR9Fymg It sounds really cool and different and I was just wondering what scale or mode he used in this song or if he modulated or something? Thanks (: