The season 5 premiere picks up where the season 4 finale left off. At Ross and Emily’s wedding, Ross has just said Rachel's name. Rachel wonders aloud whether she should go up to the altar, but Emily instructs the minister to continue the ceremony. She is clearly livid, and the newlyweds share a very cold first kiss. They walk out of the church together, and once outside, Emily violently smacks Ross in the stomach.
Everyone listens at the door.
At the reception, Ross and Emily are arguing in the bathroom while Rachel, Chandler, Joey and Monica listen at the door. Ross exits the bathroom alone, and worries that nobody seems to be having fun at his reception. He commands Joey to dance, but Joey is embarrassed and immediately stops. Emily’s stepmother’s cell phone rings, and it’s Phoebe again. She tells Mrs. Waltham that she is Dr. Phalange, Ross’s personal physician, and that Ross forgot to take his brain medicine, meaning that women’s names are interchangeable in his brain, through no fault of his own. Unfortunately, Mrs Waltham doesn't buy the story.
Chandler approaches Monica in the buffet line. The two had made plans to meet up that night, but Chandler is worried about what the secret meetings might do to their friendship. Monica wonders how they could have let this happen, and blames the fact that they are away in a foreign, romantic country. With this logic, Monica and Chandler decide that while they are still in London, it only makes sense to keep having sex. They decide to meet in the wine cellar in a few minutes.
Monica tries to make her escape to the wine cellar, but Rachel stops her, wanting to talk about Ross saying her name at the altar and what it could mean. Monica tries to get her friend to leave her alone, but when Rachel decides to talk to Ross about what he thinks it meant, Monica tries to convince her to stay away, since he is married to Emily now. Before she gets the chance to meet Chandler in the wine cellar, Monica sees Chandler reappear. They cannot meet down there to have sex as a drunken Mr Waltham (Emily’s father) is giving guided tours of the room. Monica and Chandler see Joey eating steak, even though he promised Phoebe he would not eat meat until the babies are born. He uses the excuse that they are in another country so it does not count. Monica and Chandler, having used that reason to excuse their own behavior, let him off the hook.
Ross looks at the window Emily has just escaped out of.
Rachel approaches Ross, who is still lingering outside the bathroom waiting for Emily to come out. She pries a little into what happened at the ceremony, hoping to get Ross to admit that he said her name because he still has feelings for her, but he insists it was just a mistake and that he loves Emily. Joey comes over to tell Ross that the band is waiting for his first dance with Emily, and remarks that Emily sure is taking a long time in the bathroom. Rachel jokes that when she locked herself in the bathroom at her own wedding, it was because she was trying to climb out the window and take off. Ross barges into the bathroom, and sure enough, there’s an open window and no Emily.
Monica and Chandler head up to Monica’s hotel room, but find that Rachel is already there. They almost manage to shake her off by telling her they need to change and will meet her downstairs, but then Phoebe calls the hotel room and she and Rachel talk about what Ross’s name reversal meant. Monica and Chandler decide to go “change” in Chandler and Joey’s room instead. That plan is thwarted too, however, when Joey comes home with a girl. Chandler tells Joey that he was there first and he too has a girl with him, but Joey says that he already saw him going into the room with Monica, so they have to leave.
Next stop: Ross and Emily’s honeymoon suite (apparently all the friends have keys to one another’s hotel rooms). Monica feels guilty for using her brother’s honeymoon suite, but Chandler talks her into it. However, as they pull back the covers, Ross bursts in, looking for Emily. He decides he should stay in the room in case Emily tries to find him. Monica and Chandler try to leave, but he asks them to stay and keep him company, and they can’t say no.
Chandler and Monica's plan is foiled.
Quite a while later, Ross has fallen asleep with his head in Monica's lap, so she and Chandler cannot escape. When Monica and Chandler consider having sex with Ross in the room, but a knock on the door wakes Ross up. He hopes it is Emily, but it is only her father and stepmother coming to get her things. Emily’s father tells Ross that she has gone into hiding, and never wants to see Ross again. Ross begs him to tell Emily that he will be at the airport waiting to catch the flight for their honeymoon, and he hopes Emily will be there too. Emily’s father agrees to give her the message.
Emily sees Ross get on their plane with Rachel.
Monica and Chandler are sitting next to each other on the flight back to New York. They decide that maybe it was for the best that they never got together again, as it made their one night together more special. Chandler declares that they are still over international waters. Monica goes to the bathroom, with the idea that Chandler will join her there in a minute. As soon as she leaves, however, Joey takes her seat and engages Chandler in a conversation about his future as an actor. Monica returns from the bathroom half an hour later, and Joey is still talking to Chandler.
Back at the apartment, Monica, Chandler, and Joey are greeted by Phoebe. Joey and Pheobe go home, leaving Monica and Chandler alone at last. They decide that it is a good thing that they agreed not to sleep together in New York. Monica thanks Chandler, telling him that the night in London meant a lot to her, since she was going through a hard time. Chandler reveals that the night meant a lot to him too, because Monica is "really hot". The two hug, and Chandler leaves. He comes back in a minute later, saying, “I’m still on London time, does that count?” “Oh, that counts,” Monica says, and they kiss passionately.
At the airport, Rachel is on standby for a flight to New York, when she passes Ross, sitting at his gate, waiting for Emily. It is the final boarding call for Ross and Emily’s flight to Greece, and Emily has not shown up. Rachel convinces Ross that he should go to Greece without Emily, to clear his head. Since Rachel does not have a ticket home, Ross offers her Emily’s ticket to Greece. As they board the plane, Ross realizes he has forgotten his jacket in the waiting area, so Rachel goes on ahead. As Ross goes to get his jacket, he sees Emily, who has shown up at last. However, she has just seen Rachel get on their plane, and she is not happy about it. She runs away, and Ross runs after her, leaving Rachel to fly to Greece alone.