On Scorpion Season 3 Episode 7, Team Scorpion gets a job from POTUS himself. The catch is that Walter can't be a part of it because he's been flagged as a person of interest aka a potential perpetrator of citizenship fraud. Walter has been benched, and he's got an FBI watch guard to ensure that Walter doesn't help the team out.
The rest of Team Scorpion is off to save the election! For the first time, one server is tabulating everyone's vote. The problem is that the servers are overheating, and when Team Scorpion gets to the servers, they discover something far worse. Someone hacked the servers, and they are exporting all the data, manipulating the votes, and sending them back to the server.
Team Scorpion tracks down security footage of the President's Chief of Staff being at the scene of the bug planting crime. Now, Team Scorpion doesn't believe that they can trust their FBI coworkers. It's jailbreak time!
Walter and Ralph managed to listen in to the team's coms, and once they hear that the team suspects the FBI might be in on it, they make a run for it. Walter and Ralph have to get onto Air Force One to secure the Chief of Staff's tablet and shut down the program.
Walter shuts down the program, but Sly figures out that the bug is erasing 90% of the votes. Walter knows who did it, and it isn't the White House. Of course it's at this time when Secret Service finds him aboard Air Force One.
Chinese hackers are the real ones behind the voting tampering. Don't worry. Team Scorpion is able to save the day, and POTUS is so grateful, that he rewards Team Scorpion by making Walter a US Citizen.
This means that Happy and Toby can finally can get married, and they will. Unfortunately, it will take a little while longer for them to start a family. Happy's not pregnant; her blood test was a false positive.