At the Ferry Landing

1. If you don't know about the envelope, see the previous question.
2. You'll have to get the envelope in McGinty's office.
3. But you won't be able to take it while McGinty is in his office.
4. After McGinty gets back from his meeting at the ferry landing, he drops off the envelope and leaves again.
5. Go into McGinty Salvage once he leaves.
6. The front door is locked? You'll have to find another way.
7. McGinty's also has a back door...
8. ...and a rear window.
9. Open the window, climb through it, and take the envelope.