In "All the Pretty Little Horses," Wormwood had just stopped by to listen to the jazz, but Baba Ghede calls in a favor to get him to look into a mass missing persons case.
It just so happens the people that were misplaced happen to have been possessed by the Loa at the time....
http://www.amazon.com/dp/B00W8FE3FS for Kindle. Tradeback out in two weeks.
No prior knowledge or reading of Wormwood required.