Nancy's Mysterious Letter

Nancy's Mysterious Letter, a Nancy Drew book, by Carolyn Keene is 174 pages.  Nancy has a friend named Ira who is a mailman.  She invites him into her house and he give her a letter from London and leaves his mailbag by the front door.  The mailbag gets stolen.  Ira reveals to Nancy that he believes his brother, Edgar, has stolen some money of his.  Edgar has also been threatening Ira for money.  Nancy reads the letter she received and it says that she has a possible inheritance.  The only weird thing is Nancy does not know anybody from London.  Nancy tries to locate another Nancy Drew, but can't locate her.  Then she hears that the other girl is in a play near where Nancy lives.  When she goes to see her, she can't find her.  Later, while Nancy is trying to locate the other Nancy Drew, she stumbles upon some letters.  Nancy then begins to suspect that Edgar is up to no good.