Get Annette inside the bookstore so she gives you Mullen's hat. Get inside the secret passage in the whirling and get the pinball maker's coat. Wear them both at once. Then pass a reaction speed check to be able to buy "D1ck Mullen and the Mistaken Identity" from the bookstore. Read it and talk to both Annette and Plaisance about it. Go outside and two blue orbs will appear, click on them and then interact with the book again and click on the "Modus: Mullen" option.
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