Could Deke be the key to changing the timeline? The character seems to have become increasingly important to Agents of S.H.I.E.L.D. season 5. When viewers were first introduced to Deke, he was a mercenary figure who simply helped the S.H.I.E.L.D. team survive in the future. An early plot twist actually saw Deke betray Quake, handing her over to Kasius, and while he insisted he was playing "the long game," the reality is that Deke was mostly motivated by his own selfish interests.
But it didn't take S.H.I.E.L.D. long to begin exploring the complexities of Deke's character. When he heard his father's voice on a radio, Deke's motives changed; he suddenly burned with a passion to learn the truth about his fractured world. Little by little, Deke became a "True Believer" in his own right, and was even willing to sacrifice his life in order to send S.H.I.E.L.D. home. In an entertaining twist, that sacrifice meant he got sent back to the past himself, and he remains a major character.
Recent episodes have tended to use Deke as comedy relief, but there's a lot more to him than that. Is it possible that he could be the one who saves the world?
Was Deke Part of the Original Timeline?
The S.H.I.E.L.D. team are essentially stuck in a time loop. Everything they do seems preordained, building towards the dystopian future they've already visited. It's the same principle of time-travel that Fitz posited back in season 2's "Spacetime," where he insisted that the future is as immutable as the past. Crucially, though, viewers actually know a lot more about the timeline than S.H.I.E.L.D. do. That's because of episode 8, "The Last Day," which featured a series of flashbacks (or flashforwards?) exploring the timeline. They showed the surviving S.H.I.E.L.D. agents making the Lighthouse their home, desperately attempting to keep the last of humanity alive. Surprisingly, the voice of hope was actually Melinda May, who had found a measure of peace bringing Robin up as her daughter.
Three characters were entirely absent in these flashbacks. Daisy was missing, presumably killed when her powers flared out of control and shattered the planet. Coulson was absent, a first hint at his potential death. And there wasn't a trace of Deke's presence in this original timeline.
S.H.I.E.L.D. are back in the present now, and so far the course of events has seemed as certain as a train running down the tracks. Daisy's powers have been restored; the Destroyer of Worlds project is in play, and the Particle Infusion Generator has been repaired; and Robin has been brought to the Lighthouse. All this is set against the backdrop of an impending alien invasion. But here's the catch: Deke has been essentially irrelevant to all of this. So far, the only hint that his presence is preordained was when Fitz and Simmons got married, and he chose a ring that reminded him of his grandmother's. But that's a relatively minor detail in the grand scheme of things, and we don't even know how many rings there were at the pawnbroker's to choose from in the first place.
Time May Be Trying To Correct This Anomaly
There's one other circumstantial piece of evidence that Deke may not be part of the original timeline, and it's tied to Fitz's concept of time. Agents of S.H.I.E.L.D. has previously argued that time is essentially "fixed." Once the future has been experienced, it cannot be changed. If that's the case, then Deke is essentially a temporal anomaly -something that really shouldn't exist.
Other science-fiction series have toyed with the idea of a fixed timeline as well. Conceptually, the idea is usually linked to another one; that time itself will try to correct any anomaly. In Deke's case, that should mean that he will be placed in a constant state of jeopardy, his life always under threat. That certainly seems to be the case; even when in the Lighthouse, Deke seemed to act as a magnet for apparitions from the Fear Dimension.
Events in "The Honeymoon" definitely support this theory. Deke was injured in a firefight, and Mack and Piper desperately tried to save his life. No matter what they did, another complication seemed to happen, such as a ruptured artery. Deke did ultimately survive, but it was a close thing. Was that actually time attempting to correct the anomaly, to wipe him out of existence before his impact on the timeline could grow?