Tim Bisley (Simon Pegg) and Daisy Steiner (Jessica Stevenson) meet each other in a cafe and are soon planning on moving in together. The only problem is the advert for the flat they're planning on renting is for a professional couple only. Tim suggests they pretend to be a couple. They do this and are soon living in the flat below the Landlady and above the strange man in the basement.
Brian receives an invitation to the new performance art show of his ex-partner Vulva. He plucks up the courage to go, along with Tim and Daisy, but is treated horribly by Vulva. Tim comes to the rescue after his violence tendencies are brought out by a bowl of Twiglets. Meanwhile, Daisy has a magazine interview which doesn't go too well, and the experience leads her to try a little performance art of her own.
Tim's ex Sarah calls him up and wants to get together, Tim is over the moon at the idea of them getting back together, though Mike and Daisy are less impressed and worried about him getting hurt again. Meanwhile, Mike is up for re-evaluation for the TA, and is delighted to be let back in. Tim meets up with Sarah and it turns out she really does want to try again with him, but at the last moment he sees sense and declines, not wanting to give up all his has with Daisy and his friends.
Daisy returns from her Eastern travels to find Mike has been living in her room, and that the enigmatic stranger she met on the way may have been even more mysterious than she thought. Turns out that he swapped bags with her, and she's now being followed by secret agents keen to get to the contents.
The fighting between Marsha and her daughter Amber escalates, until Amber finally storms out, leaving Marsha with an empty room. Meanwhile, Daisy is still out of work, and Tim has been fired for getting a bit too worked up about The Phantom Menace. The two of them head to the dole office together, but after Daisy is refused any money, things look bad. Especially when they arrive home to find Mike has moved upstairs into the now spare room.
Tim is delighted but nervous as anything when Damian Knox of Darkstar Comics asks him to bring in his portfolio. The last time they met, Knox cruelly put down Tim's work, hence Tim drew a less than flattering portrait of him. Daisy puts this drawing into Tim's portfolio, trying to help, and leaving Tim with a short time to retrieve the drawing, with the assistance of Mike and Tyres.
When Sophie has to cancel a date with Tim at short notice, he and Daisy decide to go out for the evening, leaving Mike and Brian in charge of walking Colin. Tim and Daisy's adventures include bumping into Tim's old enemy Duane Benzie, a group of angry teens who are trying to score, and losing their keys.
The gang go out for dinner to celebrate Daisy's birthday, and Marsha gets very suspicious as Tim flirts constantly with Sophie and seems to pay no attention to Daisy. She eventually tells Daisy that she saw the two of them kissing, leading Daisy to admit that she and Tim aren't really a couple and never were. Marsha is devastated to find out that they'd all been lying to her, and storms out of the restaurant and then the flat.
When Tim, Daisy and the others discover that Marsha has put the place up for sale, they panic and start trying to make plans to find her and win her back. Meanwhile, Daisy is offered a job on a local newspaper back home, and decides to take it, and Sophie is also leaving for a new job - though hers is in Seattle. After successfully getting through to Marsha, Tim finds the note from Daisy saying she's leaving. He is forced to send Mike to take Sophie to the airport whilst he rushes to the train station to persuade Daisy to stay.