Business is booming for the Peaky Blinders, as Shelby starts expanding both his legal and illegal operations. He plans for the future, looking at managing a race track in the South. He soon comes across some new adversaries, testing him in very different ways. Back in Birmingham, Shelby's home town is challenged by members of his family reacting to the upturn in their fortunes. A enemy from his past also returns hoping to exact their plan of revenge of biblical proportions.

Tommy hatches a plan to take control of the southern racecourses. He also meets the aristocratic May Carleton, and sees an opportunity to move up in the world. Meanwhile both Major Campbell and London gangster Darby Sabini plan Tommy's downfall.

Arthur and Michael both end up arrested and imprisoned. As Tommy's base in London is obliterated. Major Campbell has Tommy and his family under his thumb. Polly compromises herself hoping to secure Michael's freedom, but their relationship may be beyond repair at this point. Someone from Tommy's past pays him a visit, opening old wounds and leaving him to make a impossible decision.

Thomas Shelby’s wedding day has arrived at last, but while his guests enjoy the celebrations he has important business to conduct, as a mysterious stranger makes their presence known.

Responding to the Italians’ actions, Tommy is set on a path of deadly vengeance that could take him to his darkest place yet, and threatens to splinter the family. As Arthur struggles with his conscience, Linda implores him to stop his illicit work with the Peaky Blinders.

As the Russians test the Peaky Blinders men in their own distinctive and debauched way, Tommy realises that he is being seriously outmanoeuvred. Desperate for help, he rekindles a business relationship with a dangerous former acquaintance.