A woman is missing (a killer? or just afraid of being killed) who is not only a member of a hot money operation but is also the carrier of a smallpox epidemic to England, where her associate and plane seatmate has come down with it. Dr. Gregson of the public health tries and fails to put a cordon sanitaire around the outbreak and has additional personal agonies-his wife, using herself to test a new serum; his son abducted by his enemy. . . . All with the appropriate virulence and urgency.