The incriminating documents prove that Castillon is looking to expand his slaving business in the Free Marches, where slavery is illegal. Isabela plans to use the documents to blackmail Castillon. If Aveline is in the party when the documents are acquired, she will say that the documents should go to the Kirkwall City Guard, so that they can arrest his accomplices. If Aveline is not in the party when the documents are acquired, Isabela will comment that the city guard will find the documents very interesting.
Isabela offers to give the documents to Castillon in return for his ship and his promise to leave her alone. Isabela tells Hawke she thinks killing Castillon is crude and amateurish; getting rid of him peacefully means he'll be able to tell everyone how she bested him.Castillon agrees to the bargain, and swears on his mother's grave that Isabela will never hear from him again. At this point, Hawke can let the bargain go ahead or force the party to kill Castillon. If the party kills Castillon, Isabela expresses frustration that the documents are useless to her now. If Aveline is in the party, she tells Isabela that she could use them and Isabela hands them to her.