“One Door Closes” is episode fifteen of season two of Marvel’s Agents of S.H.I.E.L.D.
There are various flashbacks in this episode to when HYDRA came out against S.H.I.E.L.D. in Captain America: The Winter Soldier. In these, Bobbi, Mack and Hartley fight HYDRA for control of a carrier – a regular, sea based one, rather than a Helicarrier – commanded by Gonzales, who was seen as one of the people running the other S.H.I.E.L.D. in the previous episode, “Love in the Time of HYDRA”. The carrier in question is probably the one that Hunter escaped from.
Skye has been sent by Coulson to a remote location – one which appears to have had the Hulk in residence at some point, given how sturdily made it is, where Gordon, the eyeless teleporter, turns up for a friendly chat. It seems that he was also altered by the Kree mist.
Although Coulson doesn’t trust Mack, or Bobbi, now – and the last time S.H.I.E.L.D. was betrayed it was by HYDRA – the two of them still manage to get the new S.H.I.E.L.D. into the base. Technically, both groups are on the same side, but they are not exactly co-operating, and neither really trusts the other – generally, you don’t attack people you trust.