After most of one family on a Montana camping trip are mysteriously stricken with fever and skin rashes, Dr. Connor and Dr. Durant soon make a startling discovery -- the victims suffer from smallpox, a deadly disease thought to be eradicated. The FBI moves to track a rogue scientist suspected of unleashing the virus. As the dragnet for the dangerous biochemist and his mobile RV lab continues, Dr. Connor's team finds a dead Native American who was infected as well as shot. At the hospital, Dr. Durant bonds with the family's otherwise healthy but frightened little girl (as Brooke, guest star Laura Marano).