Kasha Kropinski

Using only an armrest, a curtain rod and a toothpick, MacGyver must fix a sabotaged train in order to protect a whistleblower who has proof that her boss is selling weapons to U.S. enemies.

Students start disappearing at Wexler College, an institution started by a mad historian/architect who believed in alternate dimensions. When the Librarians arrive, they discover a young student from the physics department is investigating the bizarre occurrences on her own. Meanwhile, Cassandra gets an offer that's difficult to turn down.

Jack and the team try to find Eric Miller (JAKE THOMAS), a 12-year-old, who was last seen in the boys' bathroom at his school. Eric's blood was found on a mirror shattered during an apparent scuffle. The investigators question the victim's parents, classmates and the school psychologist and discover that Eric was desperate to fit into the "cool" crowd, and it appears that his classmates may have harmed him in retaliation for a cruel joke.

In the Season 4 finale, a shooting at a nearby college sends TC, Jordan, Drew and Amira into the field, where they assist Rick with a deadly situation. Scott implements a new training program and locks horns with Julian. Drew struggles with frustrations about going to Army Ranger School while Shannon and TC both contemplate their future at San Antonio Memorial.