When a major event cripples Las Vegas, Gil Grissom, Catherine Willows, and Jim Brass return to help the team; DB and Sara consider the future; Lady Heather returns.
Peggy comes to a shocking realisation but isn't aware her true enemies are closer than she thought. Sousa narrows in on the truth about Peggy.
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