"Dark Flag" was first published as "Lipun Varjo" in Finnush by Arktinen Banaani (2010). The book was very well received in Finland where it drew comparisons with Graham Greene and Albert Camus. It was also applauded for its handling of the 9/11 material. This didn't stop conspiracy theorists taking the opportunity to confront the author during his succesful tour of the country in October 2010 - among other things, he was accused of working for the CIA. K has maintained that the book isn't intended to promote a particular theory.
It was then published by Heyne in Germany in January 2012, using the title, "Zuruck bleibt der Tod" (roughly, "What Remains After Death").
Initially, there was no English-language version of the book published, though it's now available as an e-book worldwide.