"bei Nacht und Nebel"

The German phrase 'bei Nacht und Nebel' means 'by night and fog'. It is from a common German expression, 'bei Nacht und Nebel davon gehen', which means to escape under cover of darkness. The phrase was appropriated by Hitler in his 'Night and Fog Decree', whereby political dissidents were rounded up by the secret police in the middle of the night.