As the 1920s begin to roar, business is booming for the Peaky Blinders gang. Tommy Shelby starts to expand his legal and illegal operations, with an eye on the racetracks of the south. Meanwhile, an enemy from Tommy's past returns to Birmingham.
Tommy offers to help Polly by searching for her children, who long ago were taken from her. In London, Tommy risks his life by meeting enigmatic leader Alfie Solomons. Meanwhile Arthur continues to feel the devastating effects of the Great War.
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.
Tommy finds out exactly what mission Major Campbell is forcing him to undertake. Arthur spearheads a ferocious takeover of London's Eden Club. Meanwhile, Polly's son Michael is welcomed into the business, and quickly experiences the dark side of the Peaky Blinders.
Tommy is caught by surprise when his powerbase in London is obliterated. As Tommy struggles to save his family and regain the upper hand, May expresses her feelings for him, and he is paid a visit by an old friend.
As derby day arrives, Tommy is faced with impossible decisions as he plans to strike back at his enemies and take the family business to another level. Meanwhile, Major Campbell has one final card to play - one that he is certain will bring about Tommy's demise.