BATHROOM
Don't be scared, just go ahead and draw the curtain to investigate the ominous sounds.
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Remove the tiny Excalibur from the soap bar.
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You will need to clean the soap off it.
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Easy to do with some hot water.
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Turn on the faucet and use the dagger under the running water.
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The first time you let hot water run you'll be too captivated by the spooky mirror message to do much. Retry if need be.
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Make sure to examine your dagger after washing.