The team members set aside their personal and romantic issues when hackers take over targeted U.S. military aircraft and war ships, pointing the weaponry at American cities.
When Walter is accidentally launched into space in a rocket, Team Scorpion must find a way to bring him home before his oxygen runs out.
A boy from Ralph's class goes missing after having a run-in with a deadly criminal; Toby comes closer to discovering the identity of Happy's husband.
A simple job at the Los Angeles Natural History Museum turns deadly when thieves steal things from a rare gem exhibit to get the materials they need to make a nuclear bomb.
Team Scorpion explores a deep cave system in an effort to prevent a bat population from harming the North American ecosystem; the team dons Halloween costumes for Walter's impending immigration inspection.
On election day, someone tries to create turmoil in the U.S. presidential election, and Team Scorpion is called to investigate.
While in Ireland for Megan's one-year memorial, Walter discovers a natural disaster at a nearby lake has created a poisonous cloud that threatens an entire village; Cabe and Toby try to ease the tension between Tim and Walter.
When Paige's estranged mother stumbles upon a forgotten nuclear reactor precariously close to exploding, she calls on the team for help.
Walter takes a perilous swim to rescue a woman trapped in the La Brea tar pits; Paige's mother maximizes Ralph's troop cookie sales.
Team Scorpion encounters gunrunners while spending Christmas Eve at an electronics-free mountain getaway; Tim makes a decision about his place on the team.
Team Scorpion is forced to freeze Cabe's body after he's seriously wounded by exploding shrapnel while on a mission in the desert.
When Team Scorpion is tricked into producing counterfeit cash for a foreign entity that intends to ruin the U.S. economy, Paige relies on her mother's skills as a grifter to save them.
Cabe's ex-wife needs the team's protection after she discovers evidence that suggests a prominent congressman's death involved foul play.
The team must recover stealth technology from a military plane that was shot down in Bosnia; Walter's sister visits with Sylvester at the garage.
Sylvester ends up in critical condition after accidentally triggering an explosion during an investigation; the team must remain focused on finding the culprit.
On Christmas Eve, a boy is trapped in a beach-side cave, where the rising tide threatens his life; the team races to find a way to save him.
The team tries to help Ralph when he is taken by the FBI for questioning after his web game play unintentionally reveals a CIA safe house's location.
The team searches for a CIA mole who has been coerced into stealing deadly chemicals; Paige shows Walter how to flirt.
The team must help an injured former Secret Service agent regain his memory in order to stop the launching of weapons of mass destruction.
The team members go under cover on a cruise ship in order to locate and disable stolen rockets; as Valentine's Day approaches, Ralph develops a crush.
The members of the team travel to Mexico when the daughter of a tech billionaire is abducted; Walter participates in an interview that leads to hurt feelings.
The team must facilitate peace discussions when a conflict in Eastern Europe threatens to escalate into World War III.
As the members of team Scorpion try to save lost hikers, their helicopter crashes, igniting a large wildfire and injuring the pilot.