The BAU travels to Chicago to investigate a series of mass murders, after teenagers in a missing persons report become the main suspects.
The team investigate when a woman is killed leaving an ice hockey game.
When a 200-year-old medicine jar shatters in a teenager's palm, she is admitted to the hospital with symptoms closely linked to smallpox; House must make a dangerous decision that puts his life in jeopardy; Wilson and Sam comfort a young patient.