The Legacy of Rachel Howells

Two blank sheets of writing paper sealed in an envelope with a postmark from Baskerville are brought to Holmes by London publisher Garrison Bolt. The addressee is Newman Musgrave. Together they must investigate why this letter, which contains a hidden secret, was sent with such urgency to a man, who unbeknown to the sender has been dead for number of years. Or is it possible that this note was never intended for the deceased man, but rather deliberately intended to fall into Holmes's hands?