With their backs against the wall and Nathaniel and Sibyl edging ever closer to eliminating S.H.I.E.L.D. from the history books, the agents must rely on their strengths to outsmart and outlast the Chronicoms. This is their most important fight, and it will take the help of friends and teammates, past and present, to survive. Watch the special two-hour series finale of “Marvel’s Agents of S.H.I.E.L.D.,” Wednesday, August 12th, on ABC. Episodes can also be viewed the next day on demand and on Hulu.