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Spoilers Ahead!
August 1940
Late one night a bombing raid lays waste to a residential area of Hastings. Joyce Davies, who has been away overnight, returns home the following morning to find her house in ruins and her husband dead. However, it is immediately apparent that Graham Davies did not die as a result of the bombing, but because someone had attacked him with a knife.***
It is early morning when Pilot Officer Andrew Foyle alights from a car outside 31 Steep Lane in Hastings and thanks the driver for the lift home. Christopher Foyle is awakened by the sound of someone moving around downstairs and on investigation finds his son rooting around in the kitchen. Andrew explains that he does not have leave, but has been posted not far from home. The two men talk as they eat breakfast. Andrew explains that he was given a lift home by Bruce Leighton-Morris, a
friend from his days at Oxford, who is a pilot working with the Crown Film Unit. He tells his dad that he has finished his training but instead of being attached to a squadron, has been sent to Hastings on a classified operation that he can't tell anyone about, including those closest to him. Andrew then looks intently at his father and remarks on the fact that he never talks about the last war. After some prompting, Foyle explains reluctantly that they were the worst three years of his life. He volunteered before conscription was introduced in 1916, went in as a private, served in France and came out as what they called a temporary officer and gentleman "only because there was nobody else left." Soberly, Andrew inquires if he ever killed anyone and, equally soberly, his father asks if he is worried about having to. 
"I suppose I have begun to think about it. Well? Did you?" Foyle stares down at his plate, remembering. He is just about to reply when there is a knock at the front door. He sighs in exasperation at the interruption and ignoring the summons for a moment says quietly, "Yes, I did. And all I can say is you get through it."
The knock comes again and as Foyle rises to fetch his jacket he asks his son to answer door, explaining that it will be his driver. Andrew is surprised to find a young woman in uniform on the doorstep and remarks that his father hadn't told him that his driver was such a pretty girl. Sam is not impressed by what she takes to be a typical cocky young pilot's response and Andrew apologises for offending her, saying that he just didn't expect to meet a WAAF driving his dad. Sam replies coolly that she was "hoping to cook or knit balaclavas for His Majesty's forces, but here I am." ***
On the way to the police station Sam tells her boss that her father is coming down to Hastings to see her. She is concerned because her father never wanted her to join the MTC and she thinks he will be equally disapproving of her working with the police.
In the station Milner greets his superior with the news about the finding of Graham Davies' body in the wreckage of his bombed house. The two police officers visit the site of the murder and Foyle finds a gold locket and chain in the dead man's clutched fist. Milner muses that it could have been worn by the killer and torn off during the attack, which could point to the culprit being a young girl, but Foyle looks dubious. An ARP warden tells them that the dead man was a married man with no children and had worked as a delivery driver. 
The wardens have taken Joyce Davies to a nearby pub and Foyle and Milner go there to talk to her. Joyce is distraught at her husband's death and the fact that she had not been there when he died. She cannot understand why anyone would want to kill him. She tells the policemen that Davies had collected art works from a London gallery called something like Wilson or Winstone and delivered them to Wales the day before. Under gentle questioning from a sympathetic Foyle, Joyce admits that she was with a man called Trevor Thompson in Brighton overnight. Her face creases with pain and she weeps as she explains that her husband was unaware of the affair. She claims that she did love him and would never have wanted to hurt him. When shown the locket, she says she has never seen it before. 
Back at the bombed house, Foyle speaks with Frank Watson, a member of the Home Guard who was on patrol in the area the previous night. The old man is hard of hearing and needs some questions repeated. He reports that around half past ten he gave directions to a man roughly Foyle's height and about the age of fifty, who was looking for Henley Terrace.
***
Wing Commander Martin Keller welcomes Andrew to the Manor, his new base near the Hastings coast. Keller is impressed with the young pilot's instructor's report, but says that flying under the Forth Bridge when training in Scotland was a stunt that risked not only his neck but also a valuable aircraft. It did, however, indicate an aptitude for low-level flying, which is why he had been assigned to the Hastings base. Keller tells Andrew that he is about to be let into the most important secret of the war, which must be shared with no one. As they drive to an RAF station on an airfield a little further up the coast, the Wing Commander explains that the staff there are involved in the development of RDF, Radio Direction Finding, also know as radar, and Andrew will be making a vital contribution to
the work. The system will make it possible to detect incoming enemy aircraft at night, in cloud, before they reach the coast. Sea Air Stations, called Chain Home, have been established all along the coast. These are directly connected to Fighter Command HQ in north London, which in turn is connected to the sector control rooms in different parts of the country that control Britain's defences. The officer responsible for the work being done in Hastings is Group Captain Alastair Graeme, who trained all the people involved. 
Inside the station, Graeme explains that they are engaged in fine-tuning and Andrew is to assist by flying a Spitfire at night at a low altitude to try to avoid being tracked by the radar system. He issues a stern warning to the young pilot that he must be sure to turn on his aircraft's IFF (Identification Friend or Foe) signal, because without it, coastal defences unaware of the exercises will believe him to be the enemy and fire at him. He shows Andrew the operations room and introduces him to three WAAF plotters who are working with radar screens, maps and graphs. ***
In his office DCS Foyle is studying the locket and chain. Milner reports that the man Joyce Davies says she was with the night her husband was killed backs up her story. Foyle is thinking of the man who sought directions and wonders if a murderer would have to ask the way to his victim's house. Milner agrees it is unlikely, but points out that it was blackout and half the signposts had been removed. Foyle points out to the sergeant that a recent repair has been made to the locket and instructs him to see if any jewellers in Hastings recognise it while he goes to the Whittington Gallery in London that they now know Davies worked for. It could be that the driver's involvement in transporting priceless Impressionist paintings had something to do with his murder.
***
Harold Smith dashes into his house in Eastbourne. He reads aloud from a newspaper the account of the finding of Davies' body and the subsequent police investigation. His wife reacts with alarm and Smith is plainly distressed. "What are we going to do?"
***
The next morning Andrew climbs into his plane and sets off on his first low flying exercise. The radar system fails to track him, although the echo from his IFF is detected. Shortly before he lands, Andrew's voice is heard over the speaker in the operations room: "This is Target Spitfire to Base. I've just dropped a bomb. You're all goners!" The young pilot rolls his Spitfire in victory and laughs.
From a window in the Manor he is watched by Wing Commander Keller, who then turns his attention back to a non-uniformed visitor called Henderson. He thanks the man for bringing something about Andrew Foyle to his attention and asks the name of the friend who was mentioned. Henderson reports that it is Bruce Leighton-Morris and that they are not planning to arrest him yet, but if they do, they will keep the Wing Commander informed. 
In the Manor, Andrew sits down to eat lunch with Sergeant Anne Roberts, one of the WAAF plotters. She compliments him on his flying skill and says they will have to try harder to catch him next time. Anne tells him that she has an aunt who runs a flower shop in Hastings whom she sometimes sees at weekends. Andrew looks at the food on his plate with evident distaste and suggests that they go out to lunch instead. While picnicking in a sunny spot in the countryside, Andrew asks Anne if she has a boyfriend and she tells him that it is none of his business. He replies, "Oh, I see. It's like everything else in this place - top secret."
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