Plot summary
After Ralph's friend Daniel, a non-verbal autistic boy, goes missing during their school field trip, Scorpion searches for him only to find that a suspicious man took Daniel's voice tablet mistaking it for his intended dead drop. They soon discover that the tablet is linked to the S6, an international mercenary ring. The team races to track Daniel before the S6 do, but arrive too late and then must save a panicked Daniel. He reveals that he opened a file on the wrong tablet, detailing an assassination plan to use smart bullets to take out a candidate running for Senate.
They work together to stop the plan, succeeding thanks to Happy's quick thinking. Toby visits Mark Collins in prison to ask him about Happy's husband and, instead of an answer, he gives Toby a riddle. Later, he finally figures out the riddle and finds out the identity of Happy's husband: Walter. Happy reveals their marriage was purely to help Walter get a green card and then reveals that she is pregnant, requesting a divorce from Walter.
Credits
Adapted from Wikipedia contributors, List of Scorpion episodes. HTML formatting and reference markers removed.