Theo Ngoni, returning to his home of Zagwa and reuniting with his family, foils an assassination attempt on Oenone Zero, who is married to General Naga and has taken the title of Lady Naga. Zero was in Zagwa to facilitate peace terms with Zagwa and the Green Storm; and suspects that the attempt was made by Green Storm soldiers still loyal to the Stalker Fang. Due to the possibility of another attempt, Zero has an incognito merchant airship prepared that will take her an alternate route to Naga. As Theo saved her life, Zero wants him to accompany her; Theo agrees, hopeful that he might meet Wren. En route, Zero's servant Rohini is revealed to be Cynthia Twite, a Green Storm spy who survived the events of "Infernal Devices", and attempts to kill her, but Theo intervenes. Cynthia escapes and downs the airship. The pair survive the crash, but Zero is captured by air-trader Napster Varley who plans to sell her to the "Traktionstadtsgesellschaft"; whilst Theo is saved from slavers by Hester Shaw and the Stalker Shrike, who is unable to kill due to Zero's tampering. After Theo informs them of Zero's capture, Hester and Shrike decide to find her, as Zero will be able to reverse Shrike's "barrier" she implemented.