Ep 1. Invasion

Foyle's War is a British detective drama set during the Second World War, which follows the investigations of detective chief superintendent Christopher Foyle. In season 4 episode 1, titled Invasion, the city of Hastings is preparing for an imminent invasion as the threat of German attacks looms.

With the possibility of an invasion high, Foyle is tasked with solving the murder of a local cartographer who had recently returned from mapping the English Channel. He quickly discovers that the dead man had been carrying state secrets, which could aid the German military in their invasion.

As Foyle delves deeper into the case, he uncovers a web of conspiracy and betrayal that implicates high-ranking officials in the war effort. With time running out, Foyle must work quickly to decipher the secret codes the cartographer had uncovered before they fall into the wrong hands.

Meanwhile, Sam Stewart, Foyle's driver and assistant, takes on a new job as a secretary for an American officer stationed in Hastings. As tensions rise between the two nations, and the threat of invasion looms large, Sam must navigate her way through a web of political and personal intrigue, putting her own safety at risk.

As the investigation heats up, Foyle finds himself under increasing pressure from his superiors to wrap up the case quickly. But with the fate of the country at stake, Foyle refuses to compromise his principles, determined to uncover the truth at any cost.

Invasion is a tense and gripping episode that offers a unique insight into life during the Second World War. The threat of invasion and the possibility of treachery at every turn create an atmosphere of tension and uncertainty that keeps viewers on the edge of their seats. With strong performances from the cast, including Michael Kitchen as Foyle and Honeysuckle Weeks as Sam, Invasion is a must-watch for fans of the series.