Star Trek: Discovery embraces long-form storytelling with each season focusing on a different mystery to be solved, and in Star Trek: Discovery season 3, the overarching mystery to be solved focuses on the Burn. To thwart Section 31’s genocidal A.I., Control, Commander Michael Burnham (Sonequa Martin-Green) guided the USS Discovery to Star Trek‘s 32nd century. 930 years in the future, Burnham soon learns that the galaxy had been fundamentally altered nearly a century earlier, when a disaster called the Burn wiped out thousands of Starfleet ships at once. Warp travel, once common, has been rendered a valuable luxury, and the United Federation of Planets seems like a myth.

It’s not the future that Commander Burnham expected to find in Star Trek: Discovery season 3. Burnham’s confident optimism gets Michael labeled a “true believer”, a mark that’s conferred with some derision by courier Cleveland Booker (David Ajala). People of the 32nd century are jaded without warp travel to unite each other. The Orion Emerald Chain fills the void left by the decimated Federation, and hoards the lion’s share of the galaxy’s dilithium to run their criminal operations. Without immediate answers, Commander Burnham makes it her personal mission to uncover the mystery of the Burn: to find out what exactly the Burn was, who caused it, and whether the effects of the Burn can be reversed.

What Was The Burn In Star Trek: Discovery & What Caused It?

The Burn changed the course of Star Trek’s distant future.

As Commander Burnham discovers, the Burn in Star Trek: Discovery was an ecological disaster on a galactic scale that affected all the active dilithium in the galaxy. 125 years earlier, the dilithium in active warp cores was rendered inert almost simultaneously, causing warp core breaches on every active warp-capable starship. Countless lives were lost, and the galaxy was never the same again. As a non-renewable resource, dilithium was already difficult to come by in the 32nd century, and the Burn only complicated the matter. Dilithium reserves were precious, so warp travel was reserved for a privileged few.

The cause of Star Trek: Discovery‘s Burn can be traced to one Kelpien, Su’Kal (Bill Irwin), who was the son of Dr. Issa (Hannah Spear), a Kelpien scientist investigating a potential source of dilithium on the planet Theta Zeta in the Verubin Nebula. Su’Kal had been exposed in utero to Theta Zeta’s dilithium deposits, which gave Su’Kal an affinity with the planet’s natural dilithium environment. Su’Kal’s emotions had a resonant effect on dilithium crystals, and the grief Su’Kal felt when his mother died rippled through the galaxy with a cry that destabilized the dilithium crystals in warp engines and caused breaches in every active warp drive.

How USS Discovery Solved The Burn’s Mystery

A Kelpien named Su’Kal was the cause of the Burn

Starfleet was more focused on applying their limited resources to urgent problems instead of investigating the cause of the Burn, but the USS Discovery’s Commander Michael Burnham wasn’t content to let the mystery of the Burn go. Burnham pursued a solution relentlessly, first exploring the possibility that Ni’Var’s experimental warp drive alternative, SB-19, was to blame. After ruling out SB-19, Burnham sought information from the black boxes of vessels that were destroyed in the Burn, and discovered the Burn wasn’t instantaneous, as previously thought. Instead, the delays in timing pointed the USS Discovery’s crew to the source of the Burn’s origin: the Verubin Nebula.

The mystery of the Burn was solved when Discovery made the jump to the Verubin Nebula to investigate, where Commander Michael Burnham, Captain Saru (Doug Jones), and Dr. Hugh Culber (Wilson Cruz) found Su’Kal surviving alone in a holographic environment inside the KSF Khi’eth. Su’Kal was emotionally damaged after living alone so long, and unwilling to recognize his rescuers as such. Frightened by a holographic monster from Kelpien folklore, Su’Kal’s fearful cries resonated in the same way that Su’Kal’s grief did a century earlier, and almost caused a second Burn to occur. Su’Kal needed an emotional connection, and Captain Saru reached out to Su’Kal, ensuring the galaxy’s safety.

What Happened To The Federation In Star Trek: Discovery’s Post-Burn Galaxy

“Commander Burnham, that hope is you.”

One of the greatest casualties after the Burn was the United Federation of Planets itself. Lack of warp drive left member worlds scattered and isolated, so the Federation faded from its former status as a greater political power, thanks to a dwindling supply of dilithium and rapid attrition of membership. With only 38 member worlds remaining, the vulnerable Federation moved its headquarters to a space station, hidden away from enemies like the Emerald Chain. The appearance of the USS Discovery turned out to be a boon to the ailing Federation since Discovery’s spore drive increased the Federation’s reach in the wake of the Burn.

The USS Discovery was instrumental in reinvigorating the United Federation of Planets by recreating connections between member worlds that had long gone stale. Visits to Earth and Trill brought the Discovery crew’s brand of 23rd-century optimism to lapsed Federation members, igniting a new hope for the future that other member worlds could be brought back into the Federation’s fold. The dilithium nursery on Theta Zeta resupplied Starfleet’s warp-driven starships for the foreseeable future, while alternatives to warp drive gained serious traction. The devastation of the Burn in Star Trek: Discovery couldn’t be reversed, but it could be repaired, thanks to the USS Discovery.