Though he no longer expected to find the mysterious envelope on Lubber's person, The Shadow hoped that other articles might produce a clue.

The mysterious envelope didn't preoccupy her thoughts.

When she was back in her hired car, Monty opened the mysterious envelope and removed a folded sheet of plain white paper.

He noticed that a number of pages were excluded from the files, as was a mysterious "envelope" mentioned in the case materials list.

The mysterious envelope, finally opened, proves to contain the long lost stocks, not the hoped for marriage certificate.

He intended to intercept them and read the contents of that mysterious envelope.

Fifty more came in a mysterious envelope, delivered by some unknown hand.

What would Cardona do if he suspected the existence of the mysterious envelope that Harry had appropriated?

With the mysterious envelope, it must go to The Shadow.

The main character, Tolea, is investigating his father's death, precipitated decades before by the arrival of a mysterious black envelope.