Jordan and Drew perform a daring rescue in the Season 4 opener. Also: Paul deals with fallout from standing up to his father; Scott dives into his professional life; a traveling nurse with a mysterious past arrives; and TC is held captive in Syria.

An amusement-park disaster results in mass-casualty victims flooding the hospital. Also, TC continues his quest to reunite with Syd; Drew reevaluates his priorities as a new father; Jordan tries to get Paul back on staff; Scott pursues a more active role in the hospital.

Jordan and Cain travel to the scene of an oil-field explosion and treat a patient with extreme injuries. Also, Drew and Paul try to save a patient's severed hand; Scott encounters a person from his past; and TC tries to help a sick Syrian child.

A patient from a distant town arrives for surgery. Meanwhile, Jordan gets creative to help a veteran in need; Drew struggles with being a working parent; Kenny learns to not worry about trivial matters; and TC joins in a daring rescue mission in Syria.

Drew faces an emergency on his flight home when passengers become sickened. Also, some staffers participate in an obstacle-course fund-raiser hosted by Akbar Gbajabiamila ("American Ninja Warrior"); Scott has an unforgettable date; TC treats a soldier.

Kenny joins Drew at his MMA veteran's support group and finds himself in the fight of his life. Jordan and Cain treat casualties from a hotel fire, while Shannon follows a hunch to help save a young victim. Paul's superstar sister, Dr. Bella Cummings, pays a visit to San Antonio Memorial and provides desperately needed support during a busy shift. Meanwhile, TC finally returns home, forcing him to deal with Topher's death.

Multiple veterans are injured and brought to the hospital. Also, a politician from Drew's past triggers flashbacks to his time in Iraq; Paul and Shannon must improvise while tending to a former POW; and a fearless photographer is treated.

A cyber attack creates chaos in the hospital. Meanwhile, Drew draws on his medical and military training to treat a critical patient, and TC joins on a SWAT drug raid. Also: TC contemplates returning to Syria to tie up loose ends.

TC and Jordan accompany a SWAT team on a raid and wind up with an emergency room full of sickened immigrants, including one with murderous intentions; and Scott pulls a dream team together to impress the Colonel in charge of setting up a combat training program. In other events, more is learned about Cain's past; Kenny shares some big news with the group; and Shannon keeps something personal from Paul.

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.