The Sherlock Holmes and Mary Russell series is well established now but for anyone who doesn't know, this supposes that Holmes met a young Oxford scholar (in the hugely enjoyable The Beekeeper's Apprentice) and took her on as a detecting partner. Eventually they married, and travelled widely following the First World War. The tale continues in DREAMING SPIES.

Holmes and Russell have been in India in 1924 and now take ship from Bombay to Japan. The cruise liner is full of travellers and Mary befriends a young Japanese woman called Sato Haruki. Sato is happy to give lessons in her language and customs. The first third of the book is taken up with shipboard life, putting in at Singapore and rounding Malay coasts, while his nosiness Holmes breaks into first-class travellers' cabins and Mary organises Shakespeare readings. Detail is minutely provided to portray shipboard life at the time, from the Marconi wires aloft to the different tea services for Indian or Chinese tea. Detailed and uneventful can, however, make for a slow read in a detective story. A girl has gone missing, but that's all.

During the second part Sato reveals herself to be a ninja, a spy rather than assassin she claims; she also claims to have seen the missing girl simply jump off the ship one night. Is she telling the truth? If so, what reason could a wealthy young woman have to kill herself? Mary is suspicious by nature and can't take her at her word. Sato remains with the married couple when they disembark in Japan, adopting local dress and habits. They decide to visit Kyoto, home of the Chrysanthemum Throne and Prince Hirohito. Perhaps not so surprisingly, the Prince turns out to have a case for the famous detective to solve.

A blackmailer, theft of a rare book and an unexpected death or two enliven the tale, before it returns to London and Oxford in pursuit of a strong climax. However I find that as with the last few books in this series, Laurie R King has compiled a historical travelogue first and a crime story second. Provided the reader is aware of this and enjoys such an agenda, with politicians of the day appearing as characters, DREAMING SPIES is an interesting and fun look at the world almost a century ago with some dire deeds and Sherlockian puzzle-solving woven around the history and local manners.