When you login to Mafia Wars you stand he chance of discovering the Mystery vault.
Once you discover the Mystery Vault you need to click on Email me the code. Once you click on email me the code you get an email with a link to click which takes you back to your Facebook page and the game. There you find another link to open the vault. Once your able to open the vault to stand to win some limited edition loot uptp 1000 Reward Points and up to 250 XP.
There maybe some technical related issues though and you find that the link is not opening. Most users recommend that you keep clicking and eventually it will open. Please share your experiences with the Mystery Vault and what loot you found etc