December 1925. When Tommy receives a mysterious letter on Christmas Eve, he realises that the Shelbys are in danger of annihilation.

As the Shelbys come to terms with the shocking events of Christmas Day, Tommy endeavours to unite his family and a bold new enemy makes his move.

It is the night of the big fight - Bonnie Gold versus Goliath. But as the bell rings and the crowd goes wild, dangers lurk in the shadows for Tommy Shelby and his family. When Changretta plays his final ace, he sets in motion a series of events that will change the Peaky Blinders forever.

Tradition weighs upon Arthur as Changretta finds a chink in the Shelby armour and Changretta continues to plan ways to continue the vendetta in the most devastating way possible.

Tommy finds himself engaged in bloody battle with Luca Changretta and his gang. Lizzie has even greater news to break. Meanwhile, an army colonel has questions for Ada about her past as a communist, and Jessie Eden confirms just how far she is prepared to go in pursuit of her cause.

The Peaky Blinders are lured by the Italians into a cat-and-mouse chase on the streets of Birmingham. As his factory lies idle, Tommy confronts the possibility that the Communists might win and he will be deemed a traitor to his class.