Gwen's friends have gathered for her hen's party at a bar and wondering where she is. She finally comes in and she had a lot of work.
Two Hours Earlier
Gwen chases a human-eating shapeshiafter into the loo. He tries to attack her but she opens fire, wounding him. She and Jack follow the trail of black blood and Gwen runs into a courtyard. The shapeshifter comes after her and knocks her to the ground. As she fumbles for her gun, the creatures bites her on the arm. Jack arrives and guns down the creature.
Gwen tells her friends the the bite is just a scratch.
The next morning Gwen wakes up and discovers that she's nine months pregnant.
Owen checks on her and confirms she was the recipient of exo-biological insemination. Jack explains that some creatures inseminate via a bite and Owen insists that she'll be fine. He plans to take her to the Hub and she'll have to be off of her feet for a couple of days, but Gwen insists she isn't going to miss her wedding. Since Owen said she'll be fine, she plans to go through with the wedding and then get the alien egg removed. She calls Rhys and says she has something to tell him.
Back at the Hub, Jack tells Owen to perform an autopsy on the dead shapeshifter and sends Tosh ahead to keep an eye on Gwen before the wedding. He sennds Ianto to get a bigger wedding dress.
Gwen shows Rhys her new pregnant state.
Ianto goes shopping and the owner thinking he's buying for himself.
Rhys blames Torchwood for what happened and wonders why they sent her out on a mission the night before the wedding. Gwen explains that they're going to remove the egg and Rhys makes plans to postpone the wedding. He insists that she's what matter but Gwen wants to marry him today no matter what.
Owen prepares to open up the shapeshifter when Tosh comes in, dressed for the wedding. He admits that weddings aren't his thing but she invites him anyway, insisting it isn't a date.
Gwen lies and tells her parents Geraind and Mary that she's pregnant. They take it in stride. Gwen and her parents go to the hotel and Barry and Brenda Williams arrive. After Brenda and Mary make a few catty remarks, they ask where Gwen is but she's slipped away. She's gone to see Rhys and explains her parents think she's going to give them a grandchild. Gwen doesn't want to shock them when they find ouit she's lost her "child." Rhys suggests they tell the truth but Gwen refuses. Jack calls and Rhys tells him to keep well out of it.
Gwen's friends Megan, Trina, and Melvyn arrive at the hotel for the wedding and meet with Banana, Rhys' best man. Tosh comes in with Gwen's wedding dress and Banana trie to flirt with her, but she makes a hasty exit to see Gwen. As Banana goes back to the liounge, Melvyn hits on a woman who seems attracted to him.
Tosh shows Gwen the dress and says that it's wonderful she's getting married. Gwen says that something wll eventually happened between her and Owen, but Tosh points out that Owen is dead.
Ianto shows Jack the new dress he's picked out. Owen runs in to show them that the shapeshifter is a Nostrovite. Jack realizes they're in triouble.
Melvyn pins a flower on the woman and accidental pricks her. She invites him to come with her for a bite. Tosh goes over to get a drink and notices that the woman left a drop of black blood on the bartop.
Megan and Trina go to see Gwen and confirm that she's pregnant.
The shapeshifter throws Melvyn onto the bed and starts to disrobe. Tosh goes looking for him and runs into Banana. When he tries to hit on her, she slams him against the wall. However, she hears the shapeshifter attack Melvyn and runs into the room, gun drawn. Melvyn is on the floor, partially eaten. When Banana comes in to see what the noise is about, the shapeshifter knocks out the distracted Tosh, grabs Banana, and considers taking him with her for tea later.
Jack explains that the Nostrovites are carnivores with a taste for human flesh. Owen explains that they mate for life and the male Nostrovite carries the egg sac, and then implants it in a host body. The female then tracks down the body and rips it open, claiming the child.
As Gwen goes up to her room, she passes the shapeshifter, who realizes that Gwen is bearin gher child.
Owen insists on going with Jack and taking the Singularity Scalpel in case he has to operate in the field to remove the egg. Ianto agrees and Jack reluctantly gives in.
As Gwen's friends figure they were drunk and didn't notice she was pregnant, Mary helps Gwen get into her dress. Gwen tries to explain what is giong on but Mary insists that Gwen will be a good mother wife. Gwen doesn't say anything and contemplates herself in the mirror, crying. Geraint comes in and she says she can't lie any more. The baby isn't Rhys'.
Barry goes to see his son and warn the wedding is turning into a nightmare. He asks Rhys if the baby is his and Rhys insists that he lvoes her and nothing else matters. They wonder where Banana is.
Tosh wakes up and discovers she's stuck with Banana in a web created by the shapeshifter and spun out on the bed.
Gwen explains to Geraint about the Cardiff Riff and how she deals with aliens and other dimensions.. She shows him the bite and explains that the "baby" is an alien. Geraint stares in horror and then goes to tell Mary that she's stressed to pieces and Gwen thinks her baby is from outer space. Brenda complains that Gwen is running late for her own wedding.
Tosh tries to reassure Banana, He yells for help despite her warning not to attract the shapeshifter. Finally she grabs... something on him and shuts him up
Geraint walks Gwen down the aisle and Brenda gasps in shock upon seeing her condition. The marriage begins.
As the rest of the team draws out into the countryside to get to the hotel in time, the female shapeshifter stares at her child. As the pastor asks if anyone objects, Jack bursts into the room and says that it has to stop. Brenda assumes that Jack is the child's father. Rhys orders Jack to get out and Jack starts to explain the danger. Meanwhile, Owen and Ianto find Tosh and free her.
Jack gets Gwen and Rhys alone and explains how Nostrovites breed. Meanwhile, the wedding party goes out into the grounds to discuss the upheaval while the shapeshifter mingles with them.
Gwen insists on continuing with the wedding, explaining that Rhy sis the only one who would stay at her side. Jack is ready to say something but they're interrupted when Megan finds Melvyn's body and starts screaming. In the chapel, Brenda and Mary are arguing when Megan runs in and announces that Melvyn is dead. Jack has Ianto jam the phone lines to contain the panic. He tells Owen to operate on Gwen over Rhys' objections and Gwen agrees. Jack and Tosh then go to find the woman that Tosh saw. Rhys stays at Gwen's side.
As the guests discover they can't call out, Jack enters and tells them he's with Torchwod. Geraint is surprised to learn that what Gwen was saying wasn't her imagination. Tosh spots the shapeshfiter, which reverts to its natural form and leaps out the window. Jack and Tosh give chase but lose her. They figure it won't get far without acquriing its child.
Owen explains that he's done a lot of work on the Singularity Scalpel since the Mayfly incident and he has it under control. Brenda knocks on the door and when Rhys lets her, she says that Jack and Tosh went after it. Owen goes to help them and calls Jack, who says that Brenda is outside with them. Jack barges in and points his gun at Brenda. However, Gwen identifies Brenda's horrible perfume and confirms she's the real thing. Rhys slugs Jack for threatening his mother and they realize the shapeshifter is outside. The shapeshifter partially reverts and grabs Mary, holding her hostage and offering her for the child. Gwen assures her mother she'll be safe and approaches the shapeshifter. When she releases Mary and goes for its child, Gwen shoots it with a gun hidden in her bouquet. The alien flees and Jack tells Owen to get Gwen ready.
As they go in, Owen sends Gwen on ahead and tells him that with one bad hand, he needs Rhys to help him. Rhys agrees and they start practicing.
Jack goes to see Gwen, who explains that she would have been married by now if she hadn't met Jack. When Jack admits she's not the only one who has been knocked off kilter, she insists Rhys is the one for her. "Jack" transforms and attacks her, and Gwen holds her off. Owen and Rhys arrive and Gwen runs out with Rhys while Owen shoots the alien repeatedly. It finally goes down and Owen approaches it, but it leaps up and grabs him. Owen tells it to kill him and do him a favor. The shapeshifter sniffs at him, realizes he's dead, and leaves.
As they flee through the grounds, Owen starts to feel the pangs of impending birth.
Owen finds Jack and the others and explains that the birthing instinct must be making the shapeshfiter unstoppable despite all the bullets they've poured into it. Jack says they need a bigger gun and goes out to the SVU.
Rhys and Gwen get to the stable and bar the door behind them. The shapeshifter slams on the door and Rhys grabs the Singularity Scalpel and prepares to follow Owen's instructions. On his first attempt, he blasts open a crate. Gwen tells him that she loves him and Rhys triggers the device. She spasms and he bends over to kiss her. They realize that the alien child is gone. The shapeshifter in her partial Brenda form busts in and Rhys says he's had enough. He grabs a chainsaw and prepares to cut her down, but the chainsaw runs out of gas. As the shapeshifter prepares to kill him, Jack opens fire and blasts the alien apart. He picks up Gwen and then places her hand into Rhys', saying the hero always gets the girl. She apologizes for spoiling everything and wonders if Rhys still wants to marry her.
Later, Gwen and Rhys are united in matrimony and kiss as the audience applauds. Afterward, everyone dances, even Owen and Tosh. Jack cuts in on Rhys, dances with Gwen, and assures her he'll keep busy while she's on her honeymoon. He compliments Rhys and says that her husband really loves him. Ianto comes over and cuts in to dance with Jack. Later, the Torchwood team and Rhys watch as everyone passes out. Jack explains that he put level six retcon in with the champagne so they remember what happened. Jack suggests that maybe Rhys and Gwen should take retcon but Gwen insists there'll be no secrets in their marriage. Rhys and Gwen depart on their honeymoon and Jack tells the others that it's time for the mopping.
The next morning, Jack returns to the Hub and blows some confetti in the air. He then goes to his desk and looks over old photos of himself and his wife of long ago.