Invasion

Invasion opens series 4 with an army arriving in a town whose own people are still short of everything. American soldiers come to Hastings to build an airfield, and their presence divides the place: David Barrett, who owns the farm at Hawthorn Cross, opposes the requisition of his land for the aerodrome, while for Susan Davies, a barmaid working locally, the Americans look like a way out of a narrow life. Captain John Keiffer commands the engineers, and he and Foyle get on well enough for Keiffer to invite Foyle to speak to his men about England and the English. Six weeks later an army friend of Milner's, Will Grayson, comes home on leave and dies in a house fire written off as an accident, and Milner, shaken, begins looking into it himself.

Davies is now pregnant by an American soldier and uses what she knows to blackmail her employer, Alan Carter, into keeping a profitable illegal still running on his property. She is then found strangled at a dance held by the American soldiers. The investigation moves through suspects in sequence: first her American boyfriend, because his dog tags were found in the dead woman's hands, then Barrett, then Barrett's nephew, who had been engaged to Davies. The case is effectively closed when Carter is arrested over the illegal still.

Foyle reaches the actual solution, which joins the two deaths. Carter killed Davies to stop her making money out of the still, because the alcohol it produced was toxic and had already killed Will Grayson. Grayson's death in the house fire was not an accident but poisoning by the still's spirits, and Davies's blackmail was keeping the trade going. The culprit, then, is the quiet man at the edge of the frame who is already in custody for a different offence, and the motive is the closing down of a trade that was killing the people who drank from it. The episode also changes the standing cast: Station Sergeant Ian Brooke is introduced as a permanent addition to the station, and Stewart is given a private life that Foyle misjudges.

The misdirection is the episode's strength, supplying two credible suspects before the culprit is disclosed, and the poisoning is the thread that connects the two deaths. Keith Barron's Barrett keeps the audience's suspicion alive without ever becoming the killer, and Zoe Tapper gives Davies an appetite for a larger life that makes her blackmail understandable rather than merely sordid. Jay Benedict's Keiffer gives the American presence a courteous face, and his scenes with Foyle over fishing, and his mention of a brother lost on the USS Reuben James, keep the culture clash from being one-sided.

The weakness is that the American-presence material settles into familiar observations about money and resentment, and the piece works better as a public-health story, since the still is killing people as well as defrauding the ration. As the opener of Series 4 Part 1, the first half of the only series ITV divided in two, it moves the setting further into the war and drew around 8.23 million viewers.