Related Clues:
- Ingrid in "Notorious," e.g.
- Unwelcome plant
- One undercover
- With 5-Down, snooping aid
- Thriller hero, often
- 'Alias' type
- One with a code name, perhaps
- Nathan Hale, notably
- Bug planter
- Do undercover work
- Plotted plant?
- CIA sort
- Agent 'embedded' in this puzzle's theme answers
- Work under cover, in a way
- Invisible ink user