Gwen is late for her hen night, as she was called in by Torchwood to chase down a shape-shifting alien. She follows it, eventually engaging him in a fight wherein he bites her arm before being killed by Jack. The next morning they discover that the alien had transferred fertilised eggs into Gwen, which have matured inside her body to the point where she now appears pregnant. Jack and Owen come round to her flat, and Jack tries to persuade her to cancel the wedding. Owen tells her that if she were going to die due to the implantation, it would have happened by now, so Gwen takes this as meaning she can continue with the wedding. Rhys arrives, and also tries to postpone the wedding but, at the insistence of Gwen, decides to have their wedding anyway, with Gwen's condition being explained away as her being pregnant with Rhys's child, as they do not want to have to explain about aliens or Torchwood.
During an autopsy of the alien creature, the team discover that it is a Nostrovite, a race of carnivourous shape shifters who hunt in pairs and mate for life. After fertilisation, the female passes the eggs on to the male, who then transfers them to a host to act as an incubator until the time is right. The female then tracks the host down, and when the egg is ready to hatch she tears the host apart to free the offspring. They realise that the mother must still be out there and that they need to hurry as it is out looking for Gwen.
Tosh arrives at the hotel where the wedding is taking place, after being sent there by Jack. Whilst asking the receptionist where Gwen's room is, the best man, nicknamed Banana Boat, tries to chat her up, and Tosh refuses to get involved, stating 'Bananas make me vomit'.
Gwen is becoming worried about going ahead, and says so to Rhys. They continue anyway, and Tosh comes into Gwen's room with a new wedding dress, as the one Gwen had to begin with obviously wouldn't fit, due to her pregnant belly.
The female Nostrovite tracks Gwen to the hotel where she is having her wedding. The Nostrovite murders the DJ, Mervin, and eats most of him. Her presence is soon detected by Tosh and Banana, as he followed Tosh. The Nostrovite decides not to eat them, but traps them on the bed in a sticky black web-like construct. She then joins the rest of the wedding party as they prepare for the ceremony.
Gwen and Rhys are standing at the altar when Jack runs in, demanding the wedding be stopped. Gwen and Rhys protest, but Jack insists, and takes Gwen and Rhys up to their room to explain about the Nostrovite. Meanwhile, Owen and Ianto find Tosh and Banana, and also Mervin's mangled, half-eaten corpse. Whilst this was going on, the bridesmaids were discussing the entrance of Jack, and wondering whether the baby was in fact Rhys's. One of the bridesmaids then goes up to the room Tosh and Banana are stuck in, and sees Mervin's body on the floor. She runs out screaming, and Jack, drawn by the screams, tells Ianto to 'contain the situation'. However, Ianto fails, and the bridesmaid screams that 'Mervin's been murdered' to the entire wedding party. The freed Tosh and Jack run down to the chapel, and Tosh points out the Nostrovite, at which point she changes into her true form (Her nails lengthen into claws, her eyes turn red, her teeth elongate into fangs, and her skin becomes mottled and develops a greenish tinge). She crashes through the window, and Tosh and Jack fire at her. They then give chase, but she is too quick, and they lose her.
Jack asks Owen how Gwen is via their communicator, and he says Barbara, Rhys's mum is with the couple. Tosh then points out to Jack Barbara chatting with Gwen's mum in the garden. Tosh and Jack race up to the couple's room, upon which point Jack calls Rhys's mum an 'ugly bitch', believing her to be the alien. Rhys punches Jack in the face when Gwen reveals it is in fact Rhys's mother. The team then race out into the garden to find the alien Barbara still chatting to Gwen's mother. They confront her, and the Nostrovite holds Gwen's mother hostage. She demands her child for Gwen's mother. Gwen walks towards her mother and the alien, but just as the Nostrovite releases Gwen's mother, she reveals she was hiding a gun beneath her bouquet, and fires several bullets into the Nostrovite. It flees temporarily.
Owen decides the best way to calm the situation is to use the singularity scalpel to destroy the eggs incubating within Gwen. He sends Gwen back to her room, but asks Rhys to wait outside for a moment with him. He then proceeds to tell Rhys about the Singularity Scalpel, and confesses, although he has been working on it, that was back when he had two good hands. He since broke a finger during the episode 'A Day In The Death' in order to show Tosh how 'broken' he was. He then teaches Rhys how to operate it.
Jack walks into Gwen's room whilst Owen and Rhys are outside. He stands behind her, and Gwen starts telling him how much she loves Rhys. He replies 'You're not the only one who met someone who knocked their world out of kilter'. Gwen turns around, and the two nearly kiss, but at the last moment Jack transforms into the Nostrovite. Owen then comes in, and shoots the Nostrovite Jack whilst Gwen runs out with Rhys. However, the Nostrovite gets up, and tries to attack Owen. However, after realising he is already dead, she loses interest, and chases after Gwen.
Rhys and Gwen flee to the stable, where Rhys barricades them in, and tells Gwen of Owen's plan to remove the egg with the Singularity Scalpel. The Nostrovite is banging on the door, trying to get in, but Rhys succeeds in removing the egg from Gwen's body. Just as the egg is vaporised, the Nostrovite enters, still impersonating Rhys's mam. She attacks Rhys, who fends her off with a chainsaw, but just as he raises it to strike, it stalls. At that moment, Jack enters and kills the creature with an extra-powerful gun from the SUV. He runs over to Gwen and picks her up, both are smiling, and drops her next to Rhys. He looks wistful, as he holds Gwen's hand out to Rhys proclaiming 'The hero always gets the girl'.
Rhys and Gwen’s wedding resumes, and the couple are successfully wed. At the reception, Rhys and Gwen notice everyone falling asleep. They realise that Jack has RetConned the entire wedding party to wipe their memories of the Nostrovite. Jack offers the couple the amnesia pills, mixed into champagne, but Gwen declines, stating that there’d 'be no secrets in this marriage'. They say their goodbyes and leave for their honeymoon, whilst thanking the Torchwood team for everything. Jack and the others proceed to clean up, Ianto stating 'That's what I love about Torchwood. By day, fighting the scum of the Earth, by night, you're the wedding fairy'. It then cuts to a shot of Jack entering the Hub alone, and blowing some confetti about. He then sits down at his desk, and retrieves an old tin box, containing various pictures from his past. He looks through them, reminiscing, but picks one up and stops. The camera zooms in, and reveals it to show him and his bride at his own wedding.
John Barrowman – Captain Jack Harkness
Eve Myles – Gwen Cooper
Burn Gorman – Owen Harper
Naoko Mori – Toshiko Sato
Gareth David-Lloyd – Ianto Jones
Kai Owen – Rhys Williams
Nerys Hughes – Brenda Williams
Sharon Morgan – Mary Cooper
William Thomas – Geraint Cooper
Robin Griffith – Barry Williams
Collette Brown – Carrie
Danielle Henry – Megan
Ceri Ann Gregory – Trina
Jonathan Lewis Owen – Banana Boat
Morgan Hopkins – Mervyn
Valerie Murray – Registrar
Pethrow Gooden – Shop Assistant
Mike Henley – Shape Shifter in toilet
Writer Phil Ford
Director Ashley Way
Script editor Gary Russell
Producer Richard Stokes
Chris Chibnall (co-producer)
Executive producer(s) Russell T. Davies
Production code 2.9
Series Series 2
Length 50 mins
Originally broadcast March 5, 2008