Link to the preview at CinemaBlend
"The clip, which comes via TV Guide does reveal that
GJemma Simmons appears to be happily employed at a Hydra lab, but it's very possible -- even likely -- that she's working undercover on behalf of Coulson.
As for the sequence above, is it me, or does this clip have that sort of cheerfully ominous tone to it, like things are a little too happy and something's not quite right. Also, did anyone else experience a major Lost flashback? "
Read the rest of the article at the source.