Safe

S4 E2: The team investigates if 15-year-old whiz kid Ryan Wallace is missing of his own accord in order to execute his elaborate plan to bomb his high school. The agents learn that the missing student is an unpopular worrier who has obsessed about safety issues since his father's fatal mugging. They initially surmise that Ryan's disappearance may have something to do with the school bullies who picked a fight with him at lunch the day prior. However, after determining that it was Ryan who wrote the ominous words "The End" on his own locker and that he created a plan to bomb the school as a means of helping them institute effective security measures, the team members wonder if he's a bomber in hiding or a victimized do-gooder. Meanwhile, a visibly weak Martin returns from his 6-week convalescence and tries to convince himself and his colleagues that he's fine.