cloak-and-dagger 
adjective
Involving or characterized by mystery, intrigue, or espionage: a cloak-and-dagger operation...
- Part of the misperception today stems from the cloak-and-dagger intrigue so prevalent in pop culture's version of international police work.
- So what did this man do to merit a cloak-and-dagger operation estimated to have cost close to £1m?
- Exactly how cloak-and-dagger are the secret prisons?
- negative confession
- negative crystal
- negative definite
- negative energy
- negative equity
- negative eugenics
- negative evidence
- negative eyepiece
- negative feedback
- negative flag
- negative g
- negative gearing
- negative geotropism
- negative glow
- negative-going
- negative growth
- negative income tax
- negative instance
- negatively
- negativeness
- negative oath
- negative option
- negative pedal
- negative phase sequence
- negative pledge