Five strangers have little in common but their choice of cafe (Balham's Tuckbox) - but they'll be forever linked together after they are kidnapped on an otherwise ordinary workday morning in London.
If this sounds like a book or movie or all-too-real incident you've seen before (I was initially reminded of Sydney's Lindt Cafe siege) Norman's skill is in creating readily identifiable characters who carry their own small and large tragedies and secrets.
Norman's interest isn't political, her skill in the five books up until now is as an astute observer of the human condition, especially when people are put under stress.
It soon becomes clear this is not a terrorist incident but the result of a domestic situation years in the making.
The five characters who helm the story are from a range of backgrounds and life situations - Abi a jaded lawyer is trying to start a family, Neil - an ex-teacher, now homeless through a gambling addiction, Mutesi a Tutsi woman from Rwanda, outwardly cheerful but inside haunted by what she endured in Rwanda's genocide; and Eliza, a police negotiator, who's struggling in her marriage to her stay-at-home partner, who will miss her son's school play as a result of one man's fatal decision to confront the cafe's owner.
While this certainly works as a siege thriller - much of the power comes from the slow reveal of the reasons behind the Ritalin-popping gunman's actions.
Norman - who has been based in New Zealand for many years - writes with a strong sense of compassion and social justice.
Like 2017's excellent See You in September - which I reviewed here - family is at the heart of Strangers - how they fracture, sustain or sometimes crumble in disastrous fashion.
At first the gunman, Sam, seems like just another disturbed criminal but Norman - who at one point in her life was a mediator and telephone crisis line listener - develops his story through a series of flashbacks outlining the reasons for his actions - while never condoning them.
She allows him some insight into his own behaviour.
"Killing another human being is a humbling experience," he tells Eliza at one point.
"Because it makes your own life less than worthless."
While his tragedy is at the center Norman also gives the other characters a voice, detailing their own trials and daily struggles - and the only quibble I have is that the stories of Eliza, Abi and Mutesi - all compelling characters - deserved more page time.
Norman doesn't do anything new here - we all have our burdens, relationships are difficult, families tricky, good people can spiral down quickly and life can change in an instant - but in a genre which often celebrates style over substance this is a compelling and moving novel which should bring Norman to a whole new world of readers.
The Secrets of Strangers
(Allen & Unwin, $32.99)