FBI: International Season 4 Episode 10 recap — What did the Russians do?

Disclaimer: This article contains major spoilers for FBI: International Season 4 Episode 10.

"Keep Calm and Deliver the Biotoxin," the newest episode of FBI: International aired on CBS on February 4, 2025. The Fly Team was in a desperate chase after the assassination of Dr. Vasily Svridov, a Russian biochemist, who was trying to jump ship with his risky biotoxin research.

The Russians, dead set on keeping this info away from the Americans, were hot on the trail of Dr. Svridov's daughter, Yulia Svridov, all across Eastern Europe. She had to get her dad's research to a scientist in the U.S. she could trust.

The Fly Team was dodging Russian agents left and right, but things got way more complicated when they realized this research wasn't just some abstract concept—it was a lethal virus that could trigger another pandemic.

This FBI: International episode was packed with twists, rescues, and a heart-wrenching sacrifice, so keep reading to know what's to come.

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FBI: International Season 4 Episode 10 recap—The Russians killed Dr. Svridov

Dr. Vasily Svridov, a Russian biochemist, was secretly collaborating with American scientists. His decision to defect pushed the Russian government over the edge, prompting them to send operatives to kill him. The assassination happened in his home, right at the moment he was giving a crucial briefcase to his daughter, Yulia.

As CBS explained, the Russians were frantic to prevent his research from falling into American hands, worried that it would shift the global balance of power.

Yulia narrowly escaped the attack, holding onto the briefcase her father had trusted her with. What was inside? It wasn't just research, but an actual bioweapon—a discovery that completely changed the nature of the mission.

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FBI: International Season 4 Episode 10 recap—Yulia’s escape and the train ambush

Having escaped her homeland, Yulia found sanctuary in Ukraine, yet the looming threat of Russian agents forced the FBI's rapid response team into action. Initially hesitant to place her faith in them, she ultimately consented to cooperate due to her father's dying wish.

Their strategy involved spiriting her out of the nation via train, but the Russians initiated a synchronized assault. Agents Smitty and Raines were drawn away, leaving Tyler Booth to confront a Russian operative all by himself.

Booth endured a harrowing struggle and emerged victorious, but Yulia, acting out of fear, attempted to flee on her own and almost died in the process. The Russians had breached the train, leaving no doubt that they were prepared to do anything to reclaim the briefcase on this episode of FBI: International.

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FBI: International Season 4 Episode 10 recap—The bioweapon twist and Tyler Booth’s departure

Safe and sound in Poland, the team finally grasped their predicament. Yulia, still chained to the case, reluctantly agreed to unlock it, in it were vials of a deadly virus. As TV Line noted, Dr. Svridov had once vowed never to create biological weapons, but the contents of the case painted a different picture.

The Russians caught up with them once more, with a phony BOLO (Be On the Lookout) alert to apprehend Raines and Yulia. This allowed their agents to eliminate local officers and grab the case on FBI: International.

Cleverly, however, the FBI had already replaced the vials, guaranteeing that neither the Russians nor the Americans could lay claim to the weapon.

During this chaos, Booth made a difficult personal decision—turning down a promotion to return home and be with his daughter. His leaving was tinged with joy and sadness, but Smitty had a touching reunion waiting for him.

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To know what happens after all this, catch FBI: International every Tuesday on CBS, or stream the latest episodes on Paramount+.

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