For James, the detective story is a twentieth-century morality play, and in her novels she deals with moral problems that confront society. Devices and Desires is set in the remote Norfolk headland called Larksoken, the site of a fictional nuclear power station. The threat of contamination from the station is ever-present, and one of the characters, Neil Pascoe, has mounted a one-man campaign, PANUP, against the dangers of nuclear power. His efforts do not have much success, but his arguments reflect many present-day concerns.

The question of terrorism enters into James's concerns. Carolyn Amphlett, the competent secretary, who does not wish to accompany Alex Mair to London, is in reality a member of a terrorist group. Her move to escape with Amy Camm is treated rather melodramatically, and the two perish in their attempt to outwit other terrorists. This treatment, criticized in many reviews, is nevertheless consistent with reality, since terrorist attacks are usually tinged with melodrama and often cause the death of innocent victims.

As in her previous novel, A Taste for Death (1986), James shows the deterioration of contemporary family life. Alex Mair, the director of the power plant, has divorced his first wife and is further disappointed in a love affair with Hilary Robarts, the murder victim. His passionate but brief affair with Amy Camm brings no stability to his emotional life. The question of abortion is also presented through Hilary, whose possible child with Alex has been aborted. She regrets this action, for emotional rather than for moral reasons, and is anxious to marry him and have another child, which she feels he owes her.

In Devices and Desires, James explicitly refers to homosexuality, which in previous works has been handled implicitly. Miles Lessingham admits to sexual desires for the young Toby Gledhill, who prefers the seductive feminine charm of Hilary Robarts. Carolyn Amphlett falsely claims a lesbian attachment to Amy Camm, which because of their subsequent disaster can never be disproved, and which leads to deep distress in Neil Pascoe and Jonathan Reeves. Homosexuality is treated without any judgment, but as a current social manifestation.

The question of sexually abused children is presented rather delicately in the childhood of Alex and Alice Mair, who let their father die without calling for help. Alex tells his sister that their father "will never do that to you again." The incident is not mentioned, but the reader understands what is meant, and is able to put Alex's emotional instability and ambition, and Alice's apparent coldness and detachment into the context of childhood abuse.

Children's problems occupy a major role in this novel. Young Timmy, Amy's illegitimate child, represents his mother's principal desire for respectability and evokes a sensitive response in Neil's apparently one-track mind, bent on destroying the nuclear power plant. Ryan Blaney's four motherless children are treated with great delicacy. Theresa is only fifteen yet she gives them a mother's care and forgives her father's excessive drinking. Even the baby and the little twins come alive in a sensitive but not overly sentimental portrayal of the struggles of poverty and single-parent households. Although the Blaneys are the object of concern for almost all of the headland, they are poorly treated by Hilary Robarts, the murder victim, who wants to take their home away from them. Ryan Blaney thus becomes a murder suspect, but it is interesting to see that even the murderer tries to give him an alibi, out of sympathy for four motherless children.

On a more positive side, the attachments of family life are quite evident in the novel. Police inspector Rickards is newly married and quite devoted to his wife who is expecting their first child. His mother-in-law, a domineering woman, insists that the baby be born near her. The young woman, Susie, eventually stands up for her rights and returns home. In contrast to her mother, she is content simply to be a wife and mother, without any career plans, an exception among women today, notes James. The Blaneys are also a close-knit family, who strongly miss their dead mother. Adam Dalgliesh frequently recalls his deceased wife and son with evident emotion.

As usual, James addresses religious issues. The title is taken from the general confession in The Book of Common Prayer. The devout Copleys contrast with the non-practicing, if not unbelieving villagers. Both Roman Catholic and Anglican faith is a presence throughout, and the general loss of religion in contemporary society is an obvious theme.