Molly Lane, a restaurant critic, has just died after suffering from a terminal disease that caused rapid deterioration of her physical and psychological faculties. At her funeral, her husband and former lovers have gathered at a crematorium in London to pay her their last respects. One of her former lovers is a composer named Clive Linley. Clive finds it unbearable to think of how horrible it must be to lose one's health so suddenly and he concludes that it is better to die than to suffer in the way in which Molly must have suffered just prior to her death. Clive asks his old friend, Vernon Halliday, who is also one of Molly's former lovers, to euthanize him if he should ever fall suddenly and irreparably ill. Vernon agrees to do so as long as Clive agrees to do the same for him.

After Molly's funeral, her husband discovers photographs of the British Foreign Secretary Julian Garmony. Molly had taken the photographs prior to her death. Molly and Julian were lovers at the time of her death and the photos depicted Julian dressed in women's clothing. The photos were clearly taken in private. George, seeing this as an opportunity to profit financially and to exact revenge over Julian, sells the photos to Vernon, whose London paper the Judge is desperately in need of a captivating story in order to improve its declining circulation. Vernon, who dislikes Julian for personal and political reasons, is more than willing to publish the potentially scandalous photos of Julian.

Before doing so, Vernon consults his old friend Clive on the matter. However, their discussion ends in a bitter argument marking the beginning of the collapse of their friendship. Vernon cites two reasons in favor of publication of the photos. First, it would expose Julian Garmony's hypocrisy since he has in the past denounced alternative sexual expressions. Second, it would greatly reduce Julian's chances of becoming Prime Minister, thereby saving the country from almost certain political, social, and economical disaster. Clive opposes publication of the photos because he thinks it is wrong to criticize or persecute someone for his sexual proclivities. Furthermore, such an action would constitute a betrayal of Molly. Thus, Clive begins to perceive Vernon as a man who lacks a certain moral sensitivity. Vernon sees Clive as a self-righteous critic, who fails to appreciate the consequences of not publishing the photos.

Leading up to the publication date, Vernon has successfully rallied his staff's support. Although many of his staff members wished to have their reservations documented in the minutes of their meetings, they expressed support for Vernon's proposal to publish the photos. They even hailed him as an editor with keen journalistic instincts.

Despite these successes, Vernon suffers a professional blow on the eve of publication. Rose Garmony, Julian's wife, holds a press conference in which she unveils one of the photos. She pledges her support for her husband and denounces Vernon. Vernon's staff, who had openly praised him for using the Garmony story to increase circulation of the Judge, quickly withdrew their support and Vernon is forced to resign. Before Vernon's disgraceful dismissal from the Judge, Clive sends Vernon a card in which the former claimed that the latter deserved to be fired. However, Vernon receives the card only after he was actually fired. He interprets the content of the card as Clive's way of rubbing salt into his fresh wounds. Feeling unjustly mistreated by his old friend; Vernon plots to extract revenge over Clive by exploiting the liberal euthanasia laws in the Netherlands and his promise to euthanize Clive.

In the meantime, Clive, who has been struggling to complete his Millennial Symphony, takes a short hiking trip in the Lake District in order to find inspiration. On one of his hikes, he witnesses a strange man attacking a woman. He chooses not to intervene. The attack occurs at a moment in which Clive is frantically trying to document a tune inspired by a birdcall. Clive decides that finishing his masterpiece is more important than rescuing a strange woman. Moreover, after he returns to London, Clive fails to report the attack because he wants to avoid becoming tangled in an investigation that would distract him from the completion of his masterpiece.

When Clive confesses to Vernon what he witnessed and his failure to intervene in the attack or report it, Vernon criticizes him for shirking his moral duties. When it occurs to Vernon that Clive might have witnessed an attack perpetrated by the notorious Lakeland rapist, Vernon puts even more pressure on Clive to report it to the authorities. When Clive refuses, Vernon, whose friendship with Clive has already soured over the Garmony photos, notifies the police that Clive has been withholding information that might be important to the arrest of the Lakeland rapist. Clive is asked to identify the alleged attacker in a police line-up, but nothing else is required of him. Clive is furious at Vernon for dragging him into this investigation. Vernon is outraged that Clive did not suffer more severe consequences for failing to be more cooperative with authorities. Vernon is all the more motivated to murder Clive and Clive seeks revenge on Vernon by plotting to murder him under the guise of assisted suicide.

Both Clive and Vernon travel to Amsterdam on business trips. They arrange to meet at a hotel. Each man consults his own Dutch doctor and arranges to have the other killed.