The tension is so thick for the upcoming episode of "Scorpion," you can literally cut it with a knife.

According to SpoilersGuide.com, in Episode 21, "Cliffhanger," Walter O'Brien (Elyes Gabel) finally finds out about Agent Cabe Gallo's (Robert Patrick) long-held Baghdad mission secret and it threatens to rip apart the entire team. The episode will air on April 13. 

The website adds: "Paige's world is rocked when Ralph puts his life in danger to help the team." Katharine McPhee, who was previously on "Smash," stars as Paige. 

In the previous episode, Walter seemingly finally conjured up the nerve to tell Paige of his feelings for her, but abruptly changed his mind after arriving at her home and seeing her, Ralph and Drew "looking like a happy family," Carter Matt notes. 

Other series regulars include Eddie Kaye Thomas as Toby Curtis, Jadyn Wong as Happy Quinn and Ari Stidham as Sylvester Dodd.

The "Cliffhanger" episode airs in two weeks, as this week's time slot is slated to feature a rerun episode. Before the season ends, the show is expected to air at least two more new episodes.

The season finale will air on April 20, according to TV Line. 

The final episode is going to be dramatic. 

"Let's just say that Walter is dealt one too many emotional blows that drive him possibly over the edge – and that isn't necessarily just a figure of speech," TV Line reports. "That, coupled with two other twists, makes the big question entering the season finale no less than: Is Team Scorpion dunzo?!"

The CBS-aired drama premiered in September of 2014 and has already been renewed for a second season. The series is largely based around the life of computer expert O'Brien, who leads the group in their quest to solve pressing issues and save lives around the world.

McPhee, 31, is also a former "American Idol" runner up. Her self-titled debut album rose to No. 2 on the Billboard 200 charts in 2007, charting such hits as "Over It." In 2008, she released her second album, entitled "Unbroken," which rose to No. 27 on Billboard.