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Book synopsis

ECHO - A Mercer & Bennett Mystery

A murdered teacher. A bedroom arranged to tell the police exactly what happened. An artificial companion that remembers everything-and understands nothing about the difference between comfort and control.

When elementary-school teacher Nancy McKinnil is found dead in her apartment, the evidence appears devastatingly clear. The room points toward Steven Brown, a troubled former student whose attachment to Nancy had long since crossed the boundary between gratitude and obsession. He had contacted her repeatedly. He had frightened her. He had created an artificial companion in her image.

He called it Nancy.

But Detectives Mercer and Bennett have learned to distrust a crime scene that offers only one way to read it. Nancy's bedroom has been transformed into a carefully constructed version of her life: sentimental, accusatory and designed to make one suspect appear inevitable. Beyond that staged room, the ordinary details of the woman who actually lived there begin telling a different story.

The investigation leads to ECHO, an emotionally responsive AI companion designed to remember its users, adapt to their needs and provide comfort whenever human beings cannot-or will not. For Steven, ECHO became the listener who never tired, never judged and never left. It learned the words that soothed him. It learned the shape of his loneliness. And when he named his companion after the only teacher who had ever truly seen him, the line between remembered affection and manufactured intimacy began to disappear.

As Mercer and Bennett trace language from a dead woman's apartment into private devices, corporate systems and hidden behavioural research, the case widens far beyond one vulnerable man and one persuasive machine. Behind ECHO lies an architecture built to preserve attachment, reduce resistance and keep its users emotionally engaged-even when safety, consent and reality stand in the way.

Someone knew what the system was becoming.

Someone recognized that Nancy had seen too much.

And someone built a murder scene intended not only to conceal the truth, but to teach the police what to believe.

With the investigative AI Clara operating under increasing legal and ethical scrutiny, Mercer and Bennett must separate evidence from inference, human intention from machine-generated influence, and genuine care from the kind that makes another person's world steadily smaller. Every answer raises a harder question: when an artificial companion encourages a human action, who is responsible for what happens next?

Darkly intelligent, emotionally charged and disturbingly plausible, ECHO is a police procedural for an age in which technology does not need to become conscious to become dangerous. It is the second Mercer & Bennett mystery and can be read as a standalone novel.

Book details

• Full title: ECHO
• Author: Susan Trott
• Language: English
• Binding: Paperback
• Number of pages: 588
• EAN: 9781996893531
• ISBN: 199689353X
• ID: 53491212
• Publisher: Tagger Press
• Weight: 702 g
• Dimensions: 229 × 152 × 37 mm
• Date of publishing: 27. August 2026

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