Sell the left-hand side
From Fallen London Wiki
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From: Dealing with your Screaming Map
It's keeping you up at night and frightening your pets. Get rid of the thing.
Game Instructions: This will let you exchange it for Presbyterate Passphrases.
Unlocked with 
1 x Screaming Map: Left-Hand Half
Success
Smartly done
Feducci has your map half, and you have his Passphrases. You can't help but wonder where he got them from.
You've lost 1 x Screaming Map: Left-Hand Half
You've gained 6 x Presbyterate Passphrase
