Under the diligent eyes of agent Jean, Palmer's intuition edges them closer to the professor while gun-for-hire former MI6 man Randall is always one step ahead. A tip-off from a key witness draws Jean and Palmer closer to the truth but their discovery only opens the door to a more chilling mystery.

Dalby challenges General Cathcart, suspecting American involvement in Dawson's abduction. Harry and Jean head to the Pacific atoll where the neutron bomb is to be tested.