After the episode Aftershocks it is clear that Bobbi Morse and Macks secret is pretty major. They infiltrated Coulsons office and located the toolbox that Fury gave to him. The two also mention a "base" they wonder if he has found. Mack also blew up on Coulson revealing his true attitude of disdain toward the director.
Who are Bobbi and Mack working for?
Option 1: Hydra - This was with Agent grant after all. However, after Bobbi helped deliver a major blow to that group it seems unlikely.
Option 2: US military - This is possible but neither Bobbi nor Mack have indicated being close to military.
Option 3: Aliens - There is a theory that Mack and Bobbi are alien imposters similar to the Marvel comic event. The comic event used Skulls but this would likely be either the Chitauri or the Kree. The Chitauri angle would be based around hidden agents that became stranded here during the invasion in the Avengers. The Kree angle could explore the Kree's history with the Inhuman and GH 325. A Kree story could help the show tie up a lot of loose ends so don't dismiss it.
Option 4: Other SHIELD or SWORD agents- I think Bobbi and Mack are working for a different SHIELD leader who does not trust Coulson. Perhaps, the mistrust is from his alien tech resurrection or general distrust stemming from Hydra's infiltration. These agents want Fury's toolbox so Coulson can not find their current base and potentially keep it for themselves.
It would not surprise me if this group has ties to the Gate House base that Coulson attacked to learn more about GH 325. This group has never been explained.
There are rumors swirling that we will learn more about Coulson and the Blue Alien Corpse whose blood was used to bring him back to life. It has been confirmed for awhile that the Blue Alien was a Kree the same race as Ronan and Korath in Guardians of the Galaxy. This SHIELD group may view Coulson with skepticism either due to this blood transfusion or do something more radical. Could Coulson actually be pure alien?
There are many theories on how Alien Coulson could actually be see -->What does TAHITI stand for?
SWORD? This SHIELD group could also very well be the MCU version of the organization SWORD. SWORD in the comics is basically the space based version of SHIELD. Myself and many others felt that the Gate House facility in Season 1 was likely a SWORD facility.
Evidence of a new group of SHIELD agents can be found in the synopsis of the future episode "Love in the time of Hydra".
Synopsis for "Love in the Time of Hydra:
"Love in the Time of Hydra” – Coulson and his team are still reeling from a shocking revelation that leaves the team fractured as they must decide what to do with one of their own. Meanwhile, Bobbi and Mack reveal their true allegiance to Hunter, while elsewhere, Ward and Agent 33 embark on a personal mission, on “Marvel’s Agents of S.H.I.E.L.D.,” Tuesday, March 29 (9:00-10:00 p.m., ET) on the ABC Television Network.
“Marvel’s Agents of S.H.I.E.L.D.” stars Clark Gregg as Director Phil Coulson, Ming-Na Wen as Agent Melinda May, Brett Dalton as Grant Ward, Chloe Bennet as Agent Skye, Iain De Caestecker as Agent Leo Fitz, Elizabeth Henstridge as Agent Jemma Simmons, Nick Blood as Lance Hunter and Adrianne Palicki as Bobbi Morse.
Guest starring are Henry Simmons as Alphonso “Mack” Mackenzie, Adrian Pasdar as Brigadier General Glenn Talbot, Edward James Olmos as Robert Gonzales, Christine Adams as Agent Weaver, Kirk Achevedo as Agent Calderon, Mark Allan Stewart as Agent Oliver, Simon Kassianides as Sunil Bakshi, Raquel Gardner as Carla Talbot, Maya Stojan as Agent 33, Landall Goolsby as Selwyn, Gigi Bermingham as Rhonda, Scott Speiser as station guard, Parisa Fakhri as Lieutenant Decker, Anna Campbell as female major, Shannon McClung as short officer, Meredith Bishop as Officer Anderson and Kieren Van Den Blink as female Lieutenant.
What does TAHITI stand for?
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