Llywellyn is the fourth book in the Oskar quartet. It takes place in the same time and place as the previous three, but new characters appear and all characters are filled in as their interactions and complexities increase. Zeke Bevan (Llywellyn), an Interior Department geochemist, is recruited by the CIA to finger Ariadne (aka Stephanie) as a terrorist, a recruitment that led to his cameo appearance in Catan Lil. Zeke and his girlfriend, Susan, try to fit their romantic relationship in with job conflicts. Marta Ginzburg, the architect of the dirty-bomb plot from Stephanie, emerges in Jordan, arranging a sale of SAMs to Hamas. The White Swan intelligence firm organizes a bank scam to trap a hacker named the Blimp, who was part of the Alvarez financial scheme (Favelito Stephanie, and Catan Lil). The Eel reappears and draws unwanted attention to himself among friends of Stephanie and Anton (Stephanie). Ariadne assumes role of chief of White Swan after the sudden passing of Inez. Zeke and Susan vacation in Abacos, run into Oskar (Favelito, Stephanie, and Catan Lil) in exile, and notify Ariadne. The rendition of Oskar back to Guatemala is planned and carried out during an otherwise carefree vacation, that is framed by diving on the reefs around Green Turtle Cay. Susan breaks up with Zeke. Ginzburg perceived as a threat to Ariadne, her young charge, Sarah (Catan Lil), and the entire White Swan organization. Ariadne meets Zeke in Paris and the two start a personal relationship. Benito and Ariadne track down Ginzburg in Lebanon and plan how to remove her as a threat. Ariadne is wounded during the ensuing assault, but wins kudos from the Israelis. Ariadne starts up a new section of White Swan aimed at helping child-victims of conflict. The precocious Sarah is growing into a teenager. She and Ariadne ride to a remote part of the Ten Ten Vilu estancia to look for ibexes. The two talk about love, guns, books, spies, truth and lies, lawyers, and life.