Unlock the Mystery: Crack the Clue on Secret Unsealing

1. Clandestinely open
2. Open in a furtive manner
3. Pry open under the radar
4. Covertly unseal
5. Crack quietly, maybe
6. Release the vapor surreptitiously
7. Underhandedly reveal by heating
8. Discreetly reveal by venting
9. Leak out in a sly way.