In a sense, Agents of S.H.I.E.L.D. season 5 has become a mystery story. Coulson and his team have become stranded in a dystopian future timeline, one in which the Earth has been destroyed - apparently by one of their own. Should they succeed in returning to their own time, they must try to prevent the planet's destruction. That's pretty hard to do without knowing just what forces shattered the Earth like an eggshell. The last few episodes may have just given viewers an answer - so let's look at the evidence.

Fearing rebellion, the Kree have carefully erased all historical records. As a result, few on the Lighthouse show any awareness of what - or who - destroyed the Earth. It's become an accepted fact, a horrific reality that overshadows the last remnant of humanity.

RELATED: How Can the Agents of SHIELD Prevent the Destruction of Earth?

But one man has worked it out. In a strange way, Deke has more experience with the ravaged planet than anyone else. He was brought up by True Believers, and no doubt heard the legends of S.H.I.E.L.D.. When he gained access to the Framework, Deke used it to recreate twenty-first century Earth. He ultimately concluded that the person responsible was Daisy herself; Quake, Destroyer of Worlds.

Now, it's worth stressing that Deke's information is questionable. The Framework was a twisted virtual reality, one in which Daisy became an outlaw, on the run from Hydra forces. No doubt Deke's recreation of the twenty-first century unwittingly absorbs some of those falsehoods. As a result, Deke will most certainly have a very confused notion of who S.H.I.E.L.D. are - one shaped in part by his childhood, and in part by the Framework's false history. Still, Deke's name for Quake seems to be a fairly popular one.

Kasius agrees with Deke's assessment. He, too, believes that Quake was the one who destroyed the Earth. Given Kasius was the one who erased all historical records, it's safe to say he knows what he's talking about. His information almost certainly didn't come from Deke; Kasius kills those who have too much knowledge of history, and Deke would be a fool to expose himself.

So, we have two sources claiming Daisy is the one who destroyed the planet. Although Deke is questionable, Kasius ironically is not.

Could Daisy Destroy a Planet?

Chloe Bennet as Daisy Johnson, aka Quake, on Agents of SHIELD

The fundamental problem with this theory is that Daisy doesn't possess that kind of power. It's true that she can harness powerful forces, and unleash them to devastating effect. She can trigger destructive tremors, and if she was near an active fault zone Quake could cause a major disaster. But could she really shatter the planet?

RELATED: Quake Is The Most Powerful Inhuman

Agents of S.H.I.E.L.D. has consistently given us a simple answer to that question: No. The more power Daisy wields, the more pain it causes her body. What's more, Daisy's powers seem to be linked to her emotional state. When she was lost in grief and rage, each use of her powers caused Daisy harm. Her bones began to splinter, and she ultimately wound up having to wear Fitz's gauntlets again. Daisy is now living with the possibility that she is actually a Destroyer of Worlds. When she gets back to her own time, there's simply no way she'll be emotionally stable enough to use her powers on such a scale.

There are only two ways Daisy could actually cause the Earth's destruction. The first is if she somehow received a power-up of some kind. The second is if her powers interacted with another force. And, crucially, one such force has just been brought into play.

Gravitonium

Gravitonium from Marvel's Agents of SHIELD

Agents of S.H.I.E.L.D. Season 1 introduced us to the rare fictional element "Gravitonium." Theorized by Doctor Franklin Hall, gravitonium has a dramatic effect on gravity around it. The element's existence was revealed in an episode entitled "The Assett," which ended with Dr. Hall tragically absorbed into a mass of gravitonium. S.H.I.E.L.D. retrieved this sample, but it unfortunately fell into the hands of Hydra.

RELATED: How Kree Monoliths Could Help the Agents of SHIELD Get Home

Gravitonium hasn't been mentioned since season 1, but there have been constant reports that the showrunners would revisit this. In February last year, producer Jed Whedon insisted this would come up again. "We would not be doing our jobs as well as we could if we left that unanswered," he noted.

The latest episode of season 5, "Together or Not At All," finally returned to the concept of gravitonium. It seems the gravitonium sample is being used to generate the Lighthouse's artificial gravity. This may just be a simple continuity reference, but it's more likely this is a hint as to the season's future direction.

Quake Plus Gravitonium

Quake Agents of SHIELD Season 5

Now season 5 has two powerful forces in play: Quake and gravitonium. The key point is that gravitonium generates powerful gravitational fields. Back in season 1, Fitz explained:

"When an electric current is applied, the gravitonium solidifies, and those gravity fields erupt randomly, changing the rules of gravity around it."

That's what happens when an electric current is applied. But what would happen if Quake's vibrational powers interacted with gravitonium? The element is dangerously unstable. "The Asset" demonstrated just how dangerous gravitonium could be; a relatively small electric charge was enough to destroy an entire building and bunker. It's very much possible Daisy's powers could trigger something far more destructive.

In the comics, Dr. Hall became the supervillain known as Graviton. Agents of S.H.I.E.L.D. has left Hall trapped inside the gravitonium for years, but it's likely he's about to return. A confrontation between Quake and Hall could actually unleash these cosmic forces, wreaking havoc on a scale S.H.I.E.L.D. haven't seen before.

Right now this is just a theory. But the fact remains that Daisy needs a power-up if she's actually going to destroy the world - and gravitonium is the most likely candidate. It's ironic that Hall attempted to destroy his gravitonium because he feared it could cause a catastrophe; if this theory is right, it actually caused the end of the world.

MORE: If Agents Of S.H.I.E.L.D. Season 6 Happens, What Would It Be About?

Agents of S.H.I.E.L.D. continues with ‘The Last Day’ on Friday, January 19.