The first half of the pilot episode focused on setting up the main plot of the series which is catching a serial killer in London. The protagonist Susan, who worked at Bletchley Park as a code-breaker during World War II, cannot ignore the killings because she notices a pattern that links all of the victims together. She brings this information to the deputy commissioner who sends out police to check an area Susan suspects a fifth victim may be located. The police return empty handed which results in Susan's research and ideas being pushed aside by the authorities. Her husband, Timothy, who is a civil servant in the Department of Transport, does not know about Susan's past as a code-breaker. He is embarrassed by her failed attempt at locating the killer with the deputy commissioner and actively insists on her forgetting the case and staying home to fulfill the role of housewife and mother to his children. His disappointment spurs her to burn he...