There are shades of John Carpenter's version of "The Thing" in the upcoming episode of "Marvel's Agents of S.H.I.E.L.D.";

four agents have been replaced by Life Model Decoys, including Coulson (Clark Gregg) and May (Ming-Na Wen,) but thanks to the shenanigans of last week's episode, we have no idea exactly who the other two may be.

RELATED: "Agents of SHIELD" Uncovers [Spoiler] is an LMD Sleeper Agent

Fan-favorite couple Fitz and Simmons (Iain De Caestecker and Elizabeth Henstridge) are working frantically to discover exactly who else has been replaced, but one, or both of them may well be the very LMDs they are looking for. At least, that certainly seemed to be the implication of a recent poster for the series.

As the captions on the show's latest promo point out "The machines are in control. Fight them, or become them." At the rate things are going, S.H.I.E.L.D. may well be staffed entirely by Inhumans and LMDs by the time we get to the end of the show's fourth season...

RELATED: Agents of SHIELD Poster Casts Doom Over FitzSimmons

Airing Tuesdays at 10 pm ET/PT on ABC, “Marvel’s Agents of S.H.I.E.L.D.” stars Clark Gregg as Agent Phil Coulson, Chloe Bennet as Daisy “Quake” Johnson, Ming-Na Wen as Melinda May, Iain De Caestecker as Leo Fitz, Elizabeth Henstridge as Jemma Simmons and Henry Simmons as Alphonso “Mack” Mackenzie.