Original air date: 10/02/2017 Runtime: 41:22 min. Team Scorpion continues to work with their nemesis, Mark Collins, in order to prevent an extinction event that could end humanity. Also, Cabe's last-minute decision while on the case leads to the possible end of his career. Josh Leonard guest stars.
Original air date: 10/16/2017 Runtime: 40:37 min. While decommissioning an old nuclear missile, a simple accident causes Team Scorpion to endure exposure to toxic vapor while trying to prevent the nuke from detonating. Also, Paige confronts Happy about constantly tagging along with her and Walter.
Original air date: 10/30/2017 Runtime: 40:31 min. At Halloween, Team Scorpion takes on a case to prove the existence of ghosts on the Queen Mary but find an all-too-real disaster when they locate a "ghost ship" on a deadly collision course. Also, Walter considers taking note of Paige's interests to benefit their relationship.
Original air date: 11/06/2017 Runtime: 41:22 min. While tracking a device that can prevent a nuclear meltdown through the Los Angeles sewers, Walter learns the nuances of listening and not offering advice to Paige. Also, Team Scorpion meets Florence (guest star Tina Majorino), their new neighbor at the garage, after she sends a mix of smelly chemicals through their shared ventilation as a warning to keep the noise down.
Original air date: 11/13/2017 Runtime: 41:44 min. For Sylvester's birthday, Team Scorpion visits a renaissance festival, but the revelry is cut short when a group tries to rob a nearby police evidence locker. Also, Paige grows weary of Walter's play-by-play of all the historical inaccuracies at the festival.
Original air date: 11/20/2017 Runtime: 43:13 min. On Thanksgiving, Team Scorpion's new neighbor, Florence (guest star Tina Majorino), joins them at sea on a mission to destroy a floating island of trash, but her flawed contribution leaves her, Walter and Happy stranded on the quickly dissolving island. Also, Toby works with Cabe to uncover the details of his father’s death that he has suppressed since he was a boy.
Original air date: 01/15/2018 Runtime: 43:13 min. Team Scorpion must work with Toby’s nemesis, Quincy Berkstead (Jeff Galfer), and his wife, Amy (Shantal VanSanten), Toby’s ex-fiancée, when they are locked inside an artificially intelligent doomsday bunker that aims to kill them. Also, Walter is distracted by his recent dream where he is married to Florence, not Paige.
Original air date: 01/22/2018 Runtime: 42:03 min. A solar storm knocks out power in Los Angeles, and Team Scorpion must help a teen pilot and his girlfriend who are lost over the Pacific without navigation or radio contact. Also, during the crisis, Walter must look after a group of Ralph's classmates, and Cabe tries to tell Allie finally that he loves her.
Original air date: 02/05/2018 Runtime: 41:34 min. On Valentine's Day, Team Scorpion must set aside their romantic plans to help a doctor and pilot trapped inside a helicopter that crashed atop a skyscraper. Also, Toby and Happy wait for news on their fertility results, and Sylvester realizes that he may have feelings for Florence.
Original air date: 02/26/2018 Runtime: 41:25 min. The geniuses of Team Scorpion turn into knuckleheads and Paige must simplify the science for them, when their mental faculties are impaired during a job to prevent the creation of a black hole. Also, Florence and Sylvester grow closer when she helps him with a special project.
Original air date: 03/19/2018 Runtime: 42:04 min. Team Scorpion heads to the bayou to track down a cagey alligator in order to stop a deadly mosquito-borne virus, and Paige teaches Walter the concept of the "white lie." Also, Walter hits Cabe with a tranquilizer gun and Toby must save his life, and Sylvester and Ralph help Patty when the mean girls at her school force her to get a dreaded tardy slip.
Original air date: 03/26/2018 Runtime: 43:14 min. Team Scorpion must use their high IQs to win a softball game when the homeland director challenges, with all of their future government contracts on the line. Also, Walter's secret night out with Florence puts Toby and Happy on edge.
Original air date: 04/09/2018 Runtime: 41:17 min. Paige's maternal side goes into high gear when Team Scorpion must save an unconscious, hypothermic boy stuck in the wheel well of their airborne airplane. Also, Walter's white lie to Paige starts to take a toll on him, and Paige realizes something's up.
Original air date: 04/16/2018 Runtime: 43:08 min. Team Scorpion heads to Northeast Africa where they must carefully navigate a minefield in order to save the lives of local villagers. Also, Paige and Walter’s relationship takes a shocking turn, and Toby and Happy make an important decision, on the fourth season finale.