After attending a formal dinner at another location, Bartlet and his staff return to the White House and experience an emergency quarantine inside the West Wing when the environmental hazard monitor detects a dangerous foreign substance. The unexpected lockdown creates odd couplings of people forced to occupy small rooms together. Isolated with Will, Toby accuses his former assistant of backstabbing Bartlet. As Secret Service agents and hazardous materials inspectors search for the source of the anomaly, the President, Fiderer (recurring guest star LILY TOMLIN) and Charlie submit to physical examinations, while in another room C.J. gives Donna strong career advice. And stuck with security adviser Kate (recurring guest star MARY McCORMACK), Josh queries her on why one of his jokes was deleted from Bartlet's speech--and gets an unexpected response.