Sully responds to a robbery, and an exchange of gunfire, at a friends jewellry store. Carlos is exposed to a mysterious illness. Maddox is shot dead in the precinct when Cruz and Santiago are taking him to central booking. Bosco is cleared to return to duty. This episode is Part 1 of a crossover with Medical Investigation that concludes on "Half Life". Neal McDonough and Kelli Williams guest star as their respective Medical Investigation characters - Stephen Connor and Natalie Durant.