Fawkes gets an injection that shuts off the quicksilver gland. But then the Agency has to find stolen "space-grown" crystals being used to make illegal drugs. So Claire and Fawkes struggle to restore invisibility to save a captured Hobbes.
Developing immunity to the anti-madness serum, Fawkes is given an untested new type before immunity becomes complete. But now it triggers stage 5 madness in less than a day, and shed quicksilver chips do the same to whoever touches them.
Claire disobeys the Official and gives Darien one last injection that fixes the gland, no more quicksilver madness. Darien goes to work for the FBI, and finds out about a plot by Crysallis. The FBI doesn't take him seriously, he needs Claire, and the Agency to stop Cryallis. The end of the series.