The Mystery of the Blue Train (Hercule Poirot #6), Agatha Christie. New York: William Morrow, 2005 (originally published in 1928).

Summary: A rich heiress carrying a rare ruby is murdered on the fashionable overnight train to the French Riviera on which retired detective Hercule Poirot happens to be riding.

Agatha Christie’s most well-known train mystery is Murder on the Orient Express (1934). This was preceded by a lesser-known train mystery, The Mystery of the Blue Train, published six years earlier. It wasn’t one of her favorites and one she struggled to write. But I thought it contained some interesting plot twists and a surprise ending that I wasn’t looking for.

The plot revolves around the murder of Ruth Kettering, daughter of American tycoon, Rufus Van Aldin. Just before departing for a trip to the Riviera on the Blue Train, a luxury, overnight train through France, she agrees to her father’s counsel to divorce her philandering husband, Derek Kettering, whose most recent “bit of stuff” is an opportunistic dancer, Mirelle. He also gives her the fabulous gift of a rare ruby, with a history of murder attached to it. Van Aldin tries to buy Derek off, which he refuses, even though he faces mounting debts with no income besides Ruth’s. The only way he will get anything from her is if she dies. He also knows Ruth has resumed an affair with the Comte de la Roche, who is a rogue and a swindler who thusfar has escaped the reach of the law.

Ruth is accompanied by her new maid, Ada Mason, who after her death, tells authorities that Ruth asked her to leave at Paris and stay at the Ritz. Katherine Grey is a single woman who has been an elder companion, whose service meant so much that she was left a sizable sum by the woman she cared for. She has decided that there are things to see and experience that are now possible. She has been invited to stay with her cousin, the Viscountess Tamplin and her daughter, who also hope to benefit from Katherine’s new found wealth. And Poirot, retired and seeking to enjoy the world, is also on the train, talks wisely to Katherine, who thinks detective stories are just something fictional people are part of. It turns out she will end up far more involved than she could have imagined. Poirot agrees to assist, as well as to work for Van Aldin, and his quiet, war veteran assistant, Major Knighton.

The case revolves around the time between when Ada left Ruth in Paris and who the tall male was seen entering and leaving Ruth’s compartment before the train passed through Lyons. Initial suspicions center around Ruth’s love, the Comte de la Roche, in league with a jewel dealer. Was this just a jewelry theft gone bad or something more? Yet Poirot is not so sure and suspicions turn to Derek. A cigarette case found in the compartment is thought to be his. Then Mirelle, who Derek has decided to ditch in his interest in Katherine, goes to Poirot and tells him that she saw Derek leave Ruth’s compartment at about the time the murder was purported to occur. Katherine also saw a man around Ruth’s compartment and possibly enter it.

One other detail troubles Poirot. Why did Ruth’s murderer not only strangle her but also strike her face with a disfiguring blow. Could Derek have done that? Katherine, who is now being pursued by both Derek and Major Knighton is drawn into Poirot’s counsels. At the risk of looking “past it” with Van Aldin, Poirot keeps looking, and particularly for a shadowy figure known as the Marquis.

As I mentioned, I wasn’t expecting the ending, which made this all the more fun. Poirot and Katherine match each other in very different ways in their own self-possession. I would have liked to see them together again–and perhaps Poirot would have as well–but she makes a different choice that, depending on your perspective, may seem “safe” or alternatively reflect a mature self-understanding. I think the latter and found her one of the most interesting of Christie’s characters, in her understated way.