Maher Arar was kidnapped, sent overseas and tortured. His lawsuit was tossed out of court because it would have revealed national security secrets.
German citizen Khalid el-Masri was similarly kidnapped and tortured in a case of mistaken identity. He was then released on a desolate road in Albania with no money, no identification, only the clothes on his back, and no passport. He was detained there as a terrorist due to his unkempt appearance and general lack of documents. He eventually sued (by video -- same mistaken identity resulted in him being denied entry to the US) which suit was dismissed. This suit was dismissed without being heard because it "would present a grave risk to national security."
The state secrets exception has a long history of being used to cover up government embarrassment. You can read more about it here: