"Code Yellow," the fourth episode of Marvel's Agents of S.H.I.E.L.D. season six, features Deke Shaw's tech company being targeted by Sarge, while a parasitic shrike threat claims the life of Agent Keller . The episode highlights Deke's misuse of S.H.I.E.L.D. technology and the introduction of a fatal alien parasite that turns hosts into crystallized, explosive beings . Detailed analysis is available at EW.com . Agents of SHIELD Season 6 Episode 4: Code Yellow Recap