Like many others, I love James Ponti’s City Spies series, and “City Spies: London Calling” is no different. There’s so much to like about the novels, including two wonderful adults and the six spy-children, the clever plots that take them around the world, the strengths and vulnerabilities of all the characters, and the unexpected twists that keep us turning the pages.

In this middle grade thriller, the sister of the newest City Spy, Cairo, is being followed. Annie is not part of the City Spy family, although her father is the parent to all the kid spies. His nickname is Mother, which is a bit confusing at first, but by this sixth novel, we are used to it. We see Annie’s masterful eluding of the thug who is following her, and she manages to disappear. Her mother, Clementine, might be working for the bad guys, Umbra, and she can’t help Annie. She thinks Annie’s attempted kidnapping was to get at her. So she asks for help.

This novel is an important one in the series, although each one not only has its own plot, but also brings forward the whole story arc of the spies and the family they’ve formed together. Clementine has been an elusive mystery throughout the novels, and in this novel, the ambiguity is somewhat cleared up. We also get to meet Annie, and see her brother, Cairo in action.

There’s humor to be had as the group is called upon to protect the wedding of a royal couple. For that they have to leave their manor home in Scotland and stay in London. Each of the spies has unique talents, and Ponti’s brilliance at creating sympathetic, likable, imperfect characters shines here. Brooklyn’s bond with the computer she created, Beny, is important. Sydney’s fashion sense provides some chuckles, and the group as a whole must overcome a devastating blow to their lives.

The story is filled with danger, spycraft, double agents, betrayal and puzzles. But together, united, they manage to save the day, stay strong, and at the same time be caring and supportive. The moral lessons that Ponti shares about family, country, doing the right thing, thinking outside the box, and supporting friends and family are values that need to be shared. And while the City Spies might all look different with various shades of skin and hair, at heart, they are family. And no one should ever forget that.

Please note: This review is based on the final, hardcover book provided by Aladdin (Simon & Schuster), the publisher, for review purposes.