Scorpion will serve up a genius vs. genius grudge match for the finale, and the stakes will be high as a familiar face works to throw Walter's world into chaos.

Team Scorpion is often tasked with saving people on the order of several dozen to several thousand, but in 'Toby or Not Toby," Homeland's best and brightest will only have one name on their minds. Mark Collins (Joshua Leonard) is back, and the former Scorpion employee will put Toby's (Eddie Kaye Thomas) life on the line.

Introduced during season 1's "Plutonium Is Forever," Mark Collins once had a spark of greatness in him. Consumed entirely by thought, Collins blew out that flame when he tumbled down the rabbit hole. Caught up in conspiracy theories and the perpetrator of near nuclear disaster, Mark is still harboring a teensy bit of ill will towards Walter (Elyes Gabel) over that time his former boss had him committed. Somehow, the troubled genius will find his way out of custody and back into the picture on April 25.

"Team Scorpion must outthink their unstable ex-Scorpion member, Mark Collins, after he kidnaps Toby and threatens to kill him unless his cunning demands are met," CBS teased on Thursday.

EnStars caught up with Thomas at WonderCon and, while he couldn't say much, the actor dropped a few interesting finale teasers.

"I wish I could just talk about the finale. I wish I could just say it," Thomas teased. "There is a very big Toby/Happy development coming that is not what you're expecting...Questions are answered and also a lot more questions will be asked. [There's] a serious cliffhanger that I think will get social media all a-flutter."

Do you think Happy (Jadyn Wong), Sly (Ari Stidham), Paige (Katharine McPhee), Cabe (Robert Patrick), and Walter will rescue Toby in time? Find out when the Scorpion airs Mondays at 9 p.m. ET! Click the video below to see a preview for the series' next episode, "Hard Knox."

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Scorpion, Television, CBS