Will there be more Walter (Elyes Gabel) and Paige (Katharine McPhee) scenes in “Scorpion” Season 3, episode 21? CBS

“Scorpion” Season 3, episode 16 centered on Team Scorpion’s mission to track down a U.S. spy before her identity is exposed to the feds.

Keep It In Check, Mate” opens with the arrival of Happy’s (Jadyn Wong) dad. Cabe (Robert Patrick) has already spoken with him and is the one who invited him without Happy’s knowledge. Understandably, the latter is not pleased with the fact that her boss went behind her back. Cabe wants Happy’s father to testify to the FBI about the death of a man named Sunny, and the latter had agreed.

Team Scorpion later discovers that Sunny is a member of the CIA. But in order to get more information about him, Walter (Elyes Gabel) and Sylvester (Ari Stidham) both have to join a chess tournament as undercover agents to save the life of a person who could follow Sunny’s fate. While at the event, Team Scorpion manages to track down Natalia, and Walter and Sylvester play against her in a game of chess. After a series of elimination games, Walter and Sylvester are pitted against each other. One of them has to lose so the other could compete against Natalia. But neither of the two competitive men wants to be the loser. In the end, Walter faces off against the guest character.

During their game, Walter sends Natalia a secret message, asking her to head to the ladies room where Paige (Katharine McPhee) is waiting for her. While there, they help Natalia escape. She and Paige later get a chance to talk about the real reason why she stayed back in Sardovia. It is later revealed that Happy’s dad had been involved in Team Scorpion’s case, so he decides to turn himself in. Happy is upset, but she eventually says goodbye to her father.

Elsewhere, Ralph (Riley B. Smith) receives two invitations to his school’s Valentine’s Day event. He cannot decide which of his two classmates he should spend time with, so he asks for Walter, Sylvester and Toby’s (Eddie Kaye Thomas) advice. Ralph also asks his mom for tips on dancing with a partner.

“Scorpion” Season 3 airs Mondays at 10 p.m. EST on CBS.