.. Making the robe stink

Well, isn't the fish shop perfect place to make the robe smell like fish.

Talk to the fishmonger. He can't sell you rotten fish. Ask him about the hanging chain and about him. ( Talk about the topics until he puts on the medication bottle on the counter. )

Interesting. And he has a command word.

Use the Haunter's Mark on the medication. You learn the command word to be: Bubblewrap.

Talk to the fishmonger so long that you get to guess the command word. Guess Bubblewrap.