Proceed only if you've seen Captain America: The Winter Soldier.
Or, proceed if you don't care about comic-book movies but do vaguely care about internet memes.
Part of the plot of the latest Marvel movie involves the reappearance of HYDRA, the once-Nazi-connected terrorist organization. At one point in The Winter Soldier, a minor character from a previous Marvel movie leans over to another person and whispers the greeting, "Hail HYDRA."
And thus #HailHydra was born. Cross it with #TrueDetectiveSeason2 and you're good to go.