The sixth in the FFSG series.

Mr and Mrs Summers commence their honeymoon in a little family-run hotel in Normandy with slightly different aims. She wants it to be the foundation of a long and happy married life; he just wants to nick a French police officer's kepi. He had a Bobby's helmet stolen from him one New Year's evening in Trafalgar Square while on crowd duty; convinced it was a French girl he had earlier chatted to, he now wants revenge.

The debate over whose aims are the more achievable are put on hold when they discover a woman's body in their bathroom. Fortunately she has been knocked out rather than killed. Unfortunately it turns out that the woman, one Amelie Courbois, is an undercover police officer who was working on a drugs sting. Even worse, the heroin she was to hand over has gone missing. To further complicate matters, she was at the wrong hotel. So no-one on the French side knew she was there. The only people who could have had access to the heroin are ... Mr and Mrs Summers.

Amelie's boss, a lugubrious Detective Inspector Georges Simenon certainly seems to think so. He keeps turning up unexpectedly with Gaspode, Amelie's dog. The Summers have breakfast at an open-air café: there is Simenon. They go for a walk on the beach; Simenon turns up. They get held up by a protest of French onion farmers; Simenon coincidentally is held up at the same place on his day off.

Then there is his domineering wife, Mrs Simenon. She too is a Detective Inspector. She too has a bad habit of appearing out of nowhere. Each time she volubly embraces Frank, and disappears as quickly as she can. Frank develops a phobia about meeting her. His wife has a horrible feeling that the Simenons' marriage might be a portent of what could happen to their own marriage.

But if the Simenons are a problem, Amelie's relatives pose their own threat. They are immensely proud of the girl, partly because she is so vacuous the fact that she has become a police officer is a miracle worthy of the title, and also because they are some of the biggest crooks in the region. They don't trust Simenon, he's a flic; they don't much trust each other. But they dote on Amelie, and this English couple are either the heroes who rescued her from the bath, or they're devious Rosbifs who have stolen the heroin while dear little Amelie was unconscious. Before making a move they need to know which.

There's uncle Jacques Pointer who just so happens to stumble into their way while they're walking along Omaha Beach. He offers to take them in his plane for an aerial view of Normandy. Although he's obviously trying to pump them for information. they accept. Which is unfortunate, as someone in another plane manages to shoot M Pointer as they're airborne, and Frank has to learn how to fly very, very quickly.

There's the drunken mugger who pulls out a knife on them. He's from Paris, an illiterate minor criminal. Someone has sent for him. But who? Amelie's other uncle, Xavier Dubons? Her black-clad grandmothers, who look the types to feed the poor with one hand while slitting the throats of their enemies with the other?

Both Mr and Mrs Summers begin their honeymoon with the unbreakable intention of it being just that, a honeymoon. Instead they realise that they might just have to solve the case of the missing heroin before they do so. Even then there is a further complication. French enquiries about their identity have caused certain people in Wellbury to believe that the Summers' marriage is over and irreparable. The word is that Mrs Summers is just never going to forgive Frank after finding him in a bath with a gorgeous young (semi-clad) French woman. So the best thing Wellbury police officers can do is to hold a welcome back party while pretending that nothing, absolutely nothing, is wrong.

Which is a good way to enrage both Mrs Summers (who knows because she's kept her lines of communication open) and Frank, who doesn't, because he can't believe that anyone from Wellbury police station would be silly enough to interfere in his private life. After all, he had taught Desk Sergeant Eric Johns and others at different times a lesson about what whirlwind such a foolhardy windy action would reap. And is more than happy to repeat their experience.

To add to the devil's brew which is brewing, Frank doesn't know that his wife is in contact with Wellbury police station, nor that she's using nicknames for those concerned. His wife doesn't know that the French security service are monitoring calls between France and Britain. The French security services don't know who The Cream Cake Man is. But he sounds dangerous. And they intend to stop him before this cream cake business gets out of hand.

Strangely enough, the immense power of a modern state's security apparatus proves to be secondary to the question a new wife has. Mrs Summers had listened to her mother's strictures on how to be a good wife. One of those had been to know which side of his plates the husband liked his peas – "Only with your father it was carrots."

Which, it has to be said, is a fair question.