Margaret Duffy Books in Order

When Ingrid Langley's husband is murdered, her former husband Patrick Gillard is the only witness and a possible suspect. His undercover intelligence work draws them into a dangerous partnership, where unresolved attraction complicates the hunt for a ruthless double agent.

Patrick Gillard and Ingrid Langley travel undercover to a Canadian coastal house protecting engineers working on naval missile controls. After suspicious deaths suggest a traitor among the guests, their mission becomes a struggle to identify the threat and survive.

A threatened defense scientist interrupts the christening of Patrick and Ingrid's son, drawing them into an investigation involving suspicious deaths and violent motorcyclists. Patrick's undercover work places him in danger and tests the couple's trust in each other.

After a colleague dies in a car bombing, Ingrid Langley and Patrick Gillard investigate the brutal murder of a senior intelligence official. Their counterespionage team confronts hostile villagers, criminals, and unsettling rituals while pursuing the connections between the deaths.

On leave from intelligence work, Patrick Gillard and Ingrid Langley answer his brother's request for help with sabotage at an outdoor survival program. Their investigation into dangerous incidents leads toward a terrorist operation and an enemy from their past.

Piers Ashley returns to his family estate after a prison sentence secretly designed to protect his undercover police identity. When his family faces blackmail and an unknown gunman wounds him, he must uncover the threat without exposing his mission.

Patrick Gillard resigns from MI5, and Ingrid Langley decides to leave intelligence work alongside him. Their departure becomes complicated when evidence suggests their former boss's supposed illness conceals imprisonment and drugging, drawing them back toward dangerous unfinished business.

A stolen reliquary and the hammer murder of an elderly woman draw private investigator Joanna Mackenzie and Inspector James Carrick into intersecting inquiries. Possible links between the crimes become more urgent when violent attacks threaten the investigators themselves.

Television documentary worker Ginny Somerville inherits a house in a remote Scottish village after her estranged father dies. Discovering a corpse in its cellar forces her to confront disturbing questions about her father and his neighbor's possible involvement in murder.

Joanna Mackenzie investigates after her lover, Inspector James Carrick, is found unconscious in a crashed car with no memory of Burns Night. A nearby producer's murder complicates the inquiry, bringing former intelligence agent Patrick Gillard into their search.

Detective James Carrick initially mistakes a recovered corpse for his friend Patrick Gillard, only to learn it is Patrick's brother Lawrence. What appears to be a case of mistaken identity develops into an increasingly dangerous investigation of the teacher's life.

Opera singer Kimberley Devlin is struck by a car and buried alive in a shallow grave. Detective Chief Inspector James Carrick investigates the attack, recognizing that the apparent accident masks a deliberate attempt against a promising young performer.

Patrick Gillard's peaceful retirement ends when he is arrested over a senior anti-terrorist officer's drowning years earlier. As damning evidence and declining health threaten him, Ingrid Langley follows puzzling new information in a determined effort to clear her husband.

After novelist Ingrid Langley consults forensic pathologist John Norton for research, he is brutally murdered at home. Ingrid, Patrick Gillard, and DCI James Carrick investigate resentments within his family as further victims raise the stakes of their inquiry.

Patrick Gillard becomes technical adviser on a film about a failed Northern Ireland operation, then replaces a murdered actor's stand-in. Ingrid's research uncovers other suspicious deaths tied to the production, prompting her to investigate before Patrick becomes another victim.

Patrick Gillard joins the police through a recruitment scheme for former servicemen, but his higher rank strains his friendship with James Carrick. A grisly local murder forces an investigation while Ingrid Langley struggles to keep professional tensions under control.

A senior detective dies in a car crash while investigating an MP's murder, raising fears that other officers are at risk. Patrick Gillard and Ingrid Langley assess the danger as another determined detective pushes ahead with her own inquiries.

Patrick Gillard and Ingrid Langley investigate killings marked by initials carved into the victims' bodies. At the same time, James Carrick asks them to trace his supposedly dead criminal father, raising the possibility that the two inquiries are connected.

With a newborn to care for and Patrick away pursuing a dangerous criminal, Ingrid discovers a body in the church vestry. A more personal crisis soon develops when evidence implicates her husband, forcing her to question the circumstances surrounding his assignment.

A much-needed holiday in Bath takes an awkward turn when Patrick meets an old flame and agrees to help her house-hunt. Ingrid joins a viewing and discovers human remains, launching the couple into another dangerous investigation.

Gang warfare in Bath suggests a London crime lord is expanding into the area, prompting James Carrick to seek Patrick and Ingrid's help. As the gang anticipates their moves, threats against Patrick's family make the investigation increasingly personal.

Ingrid attends a writers' festival in Cannes to investigate novelist Clement Hamlyn's suspected criminal connections. A related murder in England draws her and Patrick toward a dangerous network whose activities extend well beyond the author's fictional crimes.

Misunderstood schoolgirl Molly Rossiter forms a mysterious connection with a figure appearing in an illustrator's paintings, calling the presence Jim. When her violent father returns from prison, she and her family flee to Cornwall and face further hostility.

James Carrick becomes a murder suspect after a violent criminal is killed and he is found injured nearby. Patrick Gillard and Ingrid Langley investigate to clear their friend, risking conflict with their employer and encounters with a ruthless gang.

Widow Anne Peters questions whether the ashes she received belong to her husband after discovering artificial body parts he never possessed. Intrigued, Patrick Gillard and Ingrid Langley investigate the cremation discrepancy and the wider mystery it reveals.

The murder of Patrick Gillard's mentor at a heavily guarded castle draws him and Ingrid into a sensitive investigation. A former enemy, a disputed inheritance, and conflict within the National Crime Agency complicate their effort to identify the killer.

While riding near home, Ingrid finds an injured undercover police commander, and two men are later discovered hanged nearby. Patrick's supposedly safer assignment gives way to an investigation involving London criminals, local connections, and poor cooperation between agencies.

MI5 asks Patrick Gillard to investigate a former enemy recently released from prison under a changed name. Meanwhile, strangers harass his widowed mother, and a disturbing discovery raises questions about whether the threats against his family connect to the case.

Patrick Gillard is summoned out of retirement to locate a missing Metropolitan Police commander wanted over corruption. Working with Ingrid, he questions why police leaders, intelligence officers, and mobsters are all pursuing the man and the secrets he holds.

The murder of young Damien Baker draws Patrick Gillard and Ingrid Langley into an investigation of robberies and a powerful criminal sponsor. With James Carrick injured, the couple's assistance may expose connections between the gang and Patrick's insurance work.