Steve Coogan and Rob Brydon are being made up for their roles in the film Tristram Shandy.

Tristram (Steve Coogan) introduces the film and its characters, who include his uncle Toby (Rob Brydon) and Corporal Trim (who are attempting a reconstruction of the Battle of Namur, at which Toby was seriously wounded in the groin) and Susannah the maid (played by Shirley Henderson), instrumental in a serious accident to Tristram's penis when a child. It transpires that the weights from the sash window were removed to make mortars for the restaged Siege of Namur. Tristram points out that he and Toby were both effectively victims of the Battle of Namur.

However, Tristram has not yet been born. Susannah runs to fetch the midwife. Coogan explains that he is also playing Tristram's father Walter Shandy. He summons the servant Obadiah to fetch Dr Slop, as he refuses to have his son delivered by a midwife. Dr Slop arrives, and demonstrates his forceps technique with a melon in place of the baby's head. The melon is crushed. Later, those same forceps crush Tristram's nose.

The name Tristram was chosen by accident. Susanna runs to Walter to say that the baby might not live, and insisting that he be baptised. He favoured the name Trismegistus, which Susanna has turned into Tristram by the time she arrives at Elizabeth's bedchamber. Walter believes that his son is cursed from the moment of his conception.

Coogan discusses the film with Mark, the director, expressing concern about the size of his role. He meets his wife Jenny and son Stephen, and he introduces her to the production assistant Jennie (with whom he is having an affair). He is asked to test a giant womb, from which Tristram will deliver one of his monologues - Mark wants him to deliver it upside down and naked, for the sake of realism.

During a costume fitting, Coogan is worried he will look shorter than Brydon. Coogan is interviewed by Anthony H. Wilson for the electronic press kit, and they discuss the book's unfilmability.

Coogan hopes to drive to the battle scene with Jennie, but reluctantly gives a lift to Brydon. Jennie tries to discuss the novel, but it becomes clear that Coogan hasn't read it. Arriving, they are surrounded by enthusiastic members of a historical re-enactment society, led by military historian David Ingoldsby. Coogan meets his agent, who reminds him of a liaison with a lap dancer and insists that he give an interview to tabloid journalist Gary, as damage limitation.

The initial battle footage is screened, to general derision. They discuss whether they need the battle scene at all, pointing out that the fundraising was on the back of Coogan pretending to drop a hot chestnut down his trousers, a scene that was never actually filmed. The writer thinks that Uncle Toby needs more screen time, a suggestion Coogan regards with horror. He takes advantage of the facilities to run earlier shots to see if it's possible to change his shoe height without affecting continuity.

Other scenes are discussed, including the issue of finding an equivalent for the book's famous black page. They also wrangle over whether the Widow Wadman scenes should be reinstated, and debate casting Gillian Anderson. Mark rings her agent, and she's available. Brydon worries about playing a love scene with one of his idols. Coogan realises that this subplot potentially gives Brydon substantially more screen time. He complains about this to Jenny, who says there are more important things in life, such as her and the baby.

The scene with Brydon and Anderson is filmed, to great acclaim from all but Coogan, trapped in the artificial womb. During the filming of the battle scene, Jennie attempts to rekindle her affair with Coogan, but is rebuffed. He returns to the hotel room and makes love to Jenny for the first time in weeks.

The next day, the birth scene is filmed. At the rough cut screening, Gillian Anderson observes that her role has largely been deleted. Mark explains his rationale behind the other changes. In the film, the primary characters hold a philosophical debate with Parson Yorick, and Tristram is christened.