Complex sentence: Beck is called back from his holiday when an important journalist called Alf Matsson has gone missing--important because the reporter's publisher threatens to release some (unspecified) information that would be embarrassing to the Swedish government.
Split into simpler sentences: Beck is called back from his holiday when an important journalist called Alf Matsson has gone missing. Important, because the reporter's publisher threatens to release some (unspecified) information that would be embarrassing to the Swedish government.