Allison Montclair's newest historical mystery, A Royal Affair, delves into British royal secrets

In this second diverting Sparks & Bainbridge mystery, the two partners of the Right Sort Marriage Bureau take on a case for a very high-profile client, which leads them into correspondingly high-stakes political intrigue.

It’s 1946 in London, and Iris Sparks, a veteran of secret wartime espionage work, and Gwen Bainbridge, an upper-crust war widow, are several months into their joint venture. While hoping that business picks up sufficiently so they can move into a dreamy new office, they’re approached by Lady Matheson, a cousin of Gwen’s who “works for the Queen in some capacity.” She demands confidentiality before revealing her proposed assignment.

The relationship between HRH Princess Elizabeth and Prince Philip is getting serious, but obstacles stand in their way. A fellow descendant of Queen Victoria and a cousin of Greece’s king, Philip is of sufficiently royal blood, but he has sisters who married Nazis, and his mother, Princess Alice, has a troubled past. Then Lady Matheson reveals a letter she received for Elizabeth which hints at blackmail over mysterious items that Princess Alice left behind on Corfu – but she can’t reveal more details. In effect, Gwen and Iris must vet Prince Philip as a suitor for Elizabeth’s hand, but without drawing attention to the process.

The unintentional detective duo (they solved a murder in their last outing) have plenty of snarky wit, and the repartee flows fast from the outset, whether they’re interviewing a loud-talking female client or ogling the mahogany desks in their hoped-for new office. It's cleverly done, but just when it starts to feel a bit much, the tone becomes more serious as the sleuthing gets underway. Admirers of The Crown and royalty in general should appreciate the details on Prince Philip’s Greek relations, whose backstory of political power, flight, and exile isn’t widely familiar.

Iris and Gwen have a solid dynamic. While they employ their separate talents (the former’s street-smarts, the latter’s insider knowledge of the aristocracy) to further their investigation, they’re also learning from one another. In a continuing mystery series, ongoing character development is key, and Montclair’s latest satisfies on that front.

Each is growing stronger personally, too, as Gwen continues to pursue custody of her adorable young son, and Iris debates how close she wants to get to her new gangster boyfriend. Their own reflections on how they’ve changed are on-point and wryly funny. After they've wrapped up one incident with the police in an amusingly questionable way, Gwen remarks to her partner, “Appalling... we’ve become appalling people, Iris. When did that happen?”

Reading the series opener (The Right Sort of Man) is probably necessary to get the full context of this one, but that’s no hardship at all.

A Royal Affair was published by Minotaur in July; I read it from an Edelweiss e-copy (thanks to the publisher).