They were supposed to be under lock and key, in a secure storage room deep inside Europol's headquarters in The Hague. But a clutch of highly sensitive files containing the personal information of top law enforcement executives went missing last summer. Europe's law enforcement agency has been mired in a whodunit ever since. According to an internal agency note seen by POLITICO, and conversations with current and former staff, the hardcopy personnel files of Europol Executive Director Catherine...