between the north and south. this follows news that a fourth american has now been detained by pyongyang. cnn senior international correspondent ivan watson following the developments live in seoul. good morning to you, ivan. what's the latest on this last american detained in pyongyang? >> reporter: well, he's in a very serious predicament right now, dave, unfortunately. this is a man who's been identified as kim hak song. he is basically a professor who was teaching at pyongyang university of science and technology. he is the second now academic u.s. citizen who had been teaching there who's been detained by the north koreans in a little over two weeks and subsequently accused, essentially, of hostile acts against the north korean regime. the other man goes by the name tony kim, and he had also been teaching there for several weeks, and he was grabbed. and part of why this is so delicate and potentially dangerous is, of course, we've