10. Season 1, Episode 17: “Turn, Turn, Turn”
The events of the latter part of season 1 ran concurrently with Captain America: Winter Solider, with both having the villainous espionage SHIELD counterpart, Hydra, heavily featured in the main storyline. On Agents of SHIELD, Coulson and company discover that SHIELD has been infiltrated by Hydra agents, compromising dozens of missions across the world. This episode also sets up the definitive tone of the series by showing just how dark of a series it could be.
Afterward, Hydra baddie John Garrett (Bill Paxton) is taken into SHIELD custody by Victoria Hand (Saffron Burrows) and Agent Grant Ward (Brett Dalton). While transporting Garrett the Fridge (a SHIELD holding facility), Hand offers Ward the chance to kill Garrett to rid the world of him. Instead, Ward kills Hand and frees Garrett, revealing that Ward, who has been a part of SHIELD since the beginning of the show, is indeed a Hydra agent.
“Turn, Turn, Turn” lets us know that all bets are off on this show, and anything can happen to anyone at anytime. This episode also kicks off the infamous “Ward is Hydra” storyline, a betrayal that haunts the team for seasons of Agents of SHIELD to follow.