I had just opened the vault when the alarm started ringing. SCARCELY
Scarcely had I opened the vault when the alarm started ringing.
This is the first time I have ever set off an alarm while working. NEVER BEFORE
Never before have I (ever) set off an alarm while working.
I had no idea it would be so complicated to escape. LITTLE
Little did I know (that) it would be so complicated to escape.