It is Thomas Shelby's long-awaited wedding day. A mysterious visitor imperils the entire Shelby family, and Tommy finds himself pulled into a web of intrigue more lethal than anything he has yet encountered.
The episode opens with a flashback of Episode 2.6, where Thomas finds out he has a job to do for Winston Churchill and that Churchill will be in touch with him.
Thomas Shelby’s wedding to Grace Burgess is taking place at a church. Not only have all of the Shelby family and their kin been invited, but Grace’s family as well, to the detriment of the Shelbys. Grace’s family is composed of cavalry men, many Irish members of the King’s British Army. They further irritate the Shelby Family by wearing their uniforms to the wedding.
The Peaky Blinders have a meeting in the kitchen. Thomas informs the men to be on their best behaviour: no fighting, no cocaine, no telling fortunes, no racing, and more. Thomas is evidently in a state of stress (and later to be revealed, fear) as he is shouting at the Peaky Blinders in a rage not seen of him before by anyone outside the family.
Grace and Tommy have sex upstairs after she gets upset with him for being on edge. He promises that he hasn't been acting like this because of the wedding. Arthur walks in on them after they're done to tell them to come downstairs, where Ada is talking about Communism with Grace's family and another man is telling inappropriate jokes.
A refugee from Russia by the name of Anton Kaledin speaks with Polly Shelby at the dinner table, attempting to negotiate topics of business between the Russians and the Shelby Family. However, Polly turns him down due to the timing of this conversation being inappropriate.
Arthur Shelby Jr. attempts to give his best man speech at the wedding, but it falls apart, and Thomas cuts him short before he reveals a secret to Grace’s Irish family members—that Grace’s previous husband had killed himself.
Thomas takes Arthur outside and informs him that the Russians have made contact with the Peaky Blinders.
Aunt Polly approaches Anton Kaledin, telling him to give her a code name in order for him to speak to Thomas. He tells her that the code is “Constantine.”
Outside, Thomas finally speaks with Anton Kaledin and, as a distraction from his secretive conversation, he allows a race of betting on horses to take place between the Shelby family and Grace’s family. The Peaky Blinders fix the race having Johnny Dogs load a horse with morphine and water. The money won from the bets on the losing horse are to be given to the Shelby Foundation Charity for reputation—so the people of Birmingham can see Thomas giving back to the poor.
Kaledin tells Thomas he has powerful enemies who are constantly watching him and his family. Thomas asks for the money he is being given from Winston Churchill (to carry out a job), and Anton informs him that it will be brought by the Duke’s niece, ten thousand dollars in US cash. Thomas in turn tells him that he will not meet with the woman, but instead have her picked up and brought to him by the police.
Thomas instructs Arthur to have Johnny Dogs light a big fire in the woods and send Finn to watch the gates, because Moss is bringing someone.
Michael meets with a young woman who was looking for cocaine at the party earlier. Michael tells her that he doesn't do coke, but she's welcome to. She dumps it out, and he notes that she doesn't do it either, based on her inexperience.
Grace goes to Polly looking for Tommy. Grace reveals that she knows what's going on with the Russians and Churchill and Polly lets slip that it had begun tonight. Grace reminds her that she used to get information out of people for a living. Polly says that she hasn't forgotten, only Tommy has. Grace leaves to have her solo dance with Tommy.
While dancing, Grace and Tommy talk about the business. She asks him to please get it done and get away from things like this. She wants to run the foundation while he runs the tracks and sells cars. She asks him to promise her this. Tommy doesn’t, but gets around it by promising to have no guns in the house and that Charles will never see one. She tells him that she loves him, and he tells her that he loves her and promises that he will make them safe.
Sergeant Moss (who is still on the Peaky Blinders’ payroll) brings the young Duchess Tatiana Petrovna to the house. Thomas informs her that Mr. Kaledin provided the wrong code name, meaning the man must be killed by the orders of Churchill. She tries to convince him to allow her to see Kaledin, but he is upset and says no, citing that Churchill ordered for "no variations." She provides Thomas with the money and heads back to Birmingham.
Arthur confides in Thomas, not wanting to murder Kaledin, but Thomas tells him that they have no choice or else they will hang. Thomas plans to use the money to buy the wharves at Boston docks, which is why he's asked for payment in dollars.
Arthur successfully kills Anton Kaledin despite struggling with the job. John has a fighting match going on near the bonfire he'd set up. Michael has sex with the girl he'd been speaking with earlier.
A man named Ruben Oliver offers to spend the night with Polly Shelby but she turns him down.
Arthur finds Linda in the chapel alone and brings her a flower, wearing gloves to cover his bloodied hands. She reassures him. The remains of Kaledin are burned and buried as Thomas holds his son after he starts crying in the middle of the night.
The next day, the Shelby Family head back to Birmingham and meet at the business home with the rest of the Peaky Blinders, and place the money they earned the day before into a large safe, proving that the family business is thriving larger than ever.
- Thomas’s middle name is Michael and Grace’s is Helen.
- Thomas is being asked by Churchill to deliver guns to the Russian "Whites". The Whites were monarchists (white was traditionally the colour of royalty) who fought the Red Bolsheviks in a civil war after the 1917 Russian Revolution. The war was pretty much over by 1922, but let's not go there. Britain did indeed back the Whites, albeit ineffectively due to war-weariness after World War I and a lack of domestic support.
- The year is now 1924; a two year time jump from Series 2, which is set in 1922.
- Polly Shelby: "Some of us know the words."
- Thomas Shelby: “No cocaine, no sport, no telling fortunes, no racing, no fucking sucking petrol out of their fucking cars, and the main thing is – no fighting.”
- Thomas Shelby ( to Arthur Shelby): "For them, family is a weakness, and they go after them. For me, family is my strength. And there's business to be done. And I need you."
- Thomas Shelby: "Now fuck weddings, fuck speeches. You're my best man every fucking day."
- Grace’s family members: "It's full of gypsies and blacks."
- Polly Shelby (to Anton Kaledin): "My senior position within the Shelby company means I don't often have to ask permission from anyone to do anything."
- Michael Gray: "I put it all together, but I don't partake. See, I've got a bright future, you see? Mapped out."
- Polly Shelby (to Grace Burgess): "Oh, I haven't forgotten, sweetheart. It's only Thomas that's forgotten what you are."