SPOILER WARNING: This article contains major spoilers for "Principia," the latest episode of Agents of S.H.I.E.L.D.
Agents of S.H.I.E.L.D. just revealed what happened to the gravitonium they discovered in Season 1. In "Principia," the latest episode, Coulson and his team learned that General Hale got her hands on it after Hydra lost it in transit.
Gravitonium debuted in the third episode of Season 1, which also introduced scientist Franklin Hall. In the episode, Hall put his life on the line to destroy the element. Even a small amount of gravitonium is enough to toss a launch a tractor-trailer, as evidenced in "Principia," so Hall decided to destabilize the element after his nemesis Ian Quinn found a large quantity of it. Unfortunately for Hall, his attempt to destroy gravitonium ended with him being sucked inside it. The gravitonium — with Hall still inside it — was last seen in Quinn’s possession in “Beginning of the End,” the Season 1 finale. Since Quinn worked with Hydra, it's not very surprising that Hydra ultimately absconded with the gravitonium.
The S.H.I.E.L.D. agents realized they would need to track this gravitonium down when the tear into the fear dimension continued to leak their worst fears into the Lighthouse. According to Fitz, "The device that we used to seal the rift is barely strong enough. It's duct tape on the Hoover Dam. It's not going to hold."
After some digging, they discovered someone who could help: Tony "Candyman" Caine, Mack's roommate from S.H.I.E.L.D. Academy. Caine had helped some former Cybertek scientists go off the grid by faking their deaths, but -- when he realized Mack needed help -- he offered to pitch in. "You guys ever hear of Project Paperclip?" he asked, to which Coulson answered, "The secret program to recruit Nazi scientists after World War II."
"Yeah. And the exact same thing happened with Hydra. For those worthy of a second chance, it was my job to give them new identities, new lives. Erase the old ones," he explained. Using his knowledge of the program, he helped S.H.I.E.L.D. track down Dr. Joseph Getty, who had last seen the gravitonium.
"I put it on a cargo ship, the Principia, to transport it to a facility in the Pacific, but it never made it," Getty revealed. "It sank during a thunderstorm. If you want gravitonium, you're going to have to reach five miles down into the ocean to get it."
However, when Fitz conducted a thorough search of the ocean floor, he couldn't find it. Fortunately, Deke quickly came up with the answer: "You need to look up in the sky... What if the ship can fly? It was carrying gravitonium during a storm! If it got hit by lightning --"
"It would charge the gravitonium," Fitz finished for him, to which Simmons added, "And generate an anti-gravity field around the entire ship."
By analyzing wind and weather patterns starting from the night it disappeared, Fitz and Simmons were able to track the ship down. Like Deke had suggested, it was indeed floating among the clouds. Daisy, Coulson and Mack quickly boarded the ship, where they found the crew long dead of severe hypoxia.
After a quick search, Coulson, Daisy and Mack discovered an empty plastic crate that once contained the gravitonium. "It looks like someone's been here before us. Whoever they were, they didn't go home empty-handed," Coulson said. They would later realize General Hale had the gravitonium, as she left some of her robot combatants on board to do away with any trespassers.
Fortunately for S.H.I.E.L.D., Hale had left a little gravitonium on board to keep the ship afloat: "It's about the size of a softball. Must've got separated from the rest." With some advice from Deke, Mack was able to trap the gravitonium in a plastic box and they were able to take it back to their base -- but not before they were attacked by Hale's robots, which tipped them off as to where the rest of the gravitonium had gone: "I think it's safe to say that General Hale has the rest."
S.H.I.E.L.D.'s visit to the Principia didn't go unnoticed. "General Hale, some of the old sleeper mechs recently came back online," Hale's assistant Candice Lee revealed to her boss later on. "The ones you left on the Principia, in case anyone found them. We should have blown that out of the sky when we had the chance."
"No, it was too risky. We don't know enough about the gravitonium. It could have responded like a nuclear reactor and set the ozone on fire," Hale responded, explaining the reason she left the Principia where it was. She also confirmed that she believes S.H.I.E.L.D. was behind the unexpected visit to the Principia.
Airing Fridays at 9 p.m. ET/PT on ABC, Marvel’s Agents of S.H.I.E.L.D. Season 5 stars Clark Gregg, Ming-Na Wen, Chloe Bennet, Henry Simmons, Ian De Caestecker, Natalia Cordova-Buckley and Elizabeth Henstridge.