Colonel and Dolly Bantry live a peaceful and predictable life in the small village of St. Mary Mead. Then one morning they discover a dead body in their library! The body is a young girl with platinum-blonde hair and a spangly dress—a body that meets the description of a girl reported missing from Danemouth, a fashionable nearby watering hole. Mrs. Bantry convinces her friend Miss Jane Marple to go to Danemouth to investigate the matter.

It turns out that the missing girl, Ruby Keene, was about to be adopted by a wealthy older man, Conway (Jeff) Jefferson, who was staying at the resort hotel. Jeff would have settled £50000 on Ruby if the adoption had been completed. Jeff has a daughter-in-law, Abby, who was married to Jeff’s deceased son, and a son-in-law, Mark, who was married to Jeff’s deceased daughter—both are with him at the hotel. At first, they are the obvious suspects, because with Ruby’s death, they would be the recipients of Jeff’s fortune when he dies. Neither one can pretend that he or she liked Ruby or was sorry about her death.

Josie Turner, on the other hand, had a vested interest in keeping Ruby alive and in favor with Jeff. Josie was Ruby’s cousin and the dance and bridge hostess at the hotel. When she twisted her ankle, she got Ruby to come to the hotel and fill in as the dance hostess. She encouraged the friendship that developed between Ruby and Jeff, but suspected Ruby of having unsuitable boyfriends that might ruin her chances.

The police soon establish that Ruby was alive and dancing at the hotel through about midnight, but before her midnight showcase dance, went to her room to "rest"—but when Josie and Raymond Starr, Ruby's dance partner, went to look for her, she was nowhere to be found. At that time, Abby, Mark, Jeff, and Josie were playing bridge in the public room. With the obvious suspects accounted for, the police (including our old acquaintance Inspector Slack) try to find the killer. But who should beat them to the punch and arrange the "trap" that blows the whole case open, but good ole Miss Marple!

Spoilers ahead! Scroll down for full spoilers of this book.

The person who killed Ruby Keene was . . . Mark Gaskill! (With the help of Josie, his secret wife.)

The story starts when Mark and Josie are having a secret affair. They get married but don’t tell anyone; Mark thinks it would influence Jeff to cut him out of the will. But then, Josie brings her cousin Ruby to be a dancer at the hotel, and the unthinkable happens: Jeff falls in love (in a way) with Ruby, and announces that he is going to adopt her and settle his fortune on her! Josie and Mark quickly formulate a plan to get Ruby out of the picture.

First, they make it seem that Ruby is having a fling with a theatrical young man named Basil Blake, who sometimes comes to the hotel. Then they find another young girl whose body type is similar to Ruby’s, and convince her that Mark is a movie agent who wants her to "test" for a movie role. They bleach her hair to match Ruby’s, put one of Ruby’s dresses on her, and then knock her out with a sleeping potion. Mark drives the girl to Basil Blake’s cottage in St. Mary Mead and strangles her on the hearth of his fireplace. All this time, Ruby is still alive and visible to all.

Then, following Josie's orders, Ruby goes to her room sometime before the midnight exhibition dance to meet Josie. Josie knocks her on the head and leaves her in her (Josie's) room. Mark and Josie then establish their alibis by playing cards until long after Ruby has "disappeared." When Josie and Raymond search for Ruby, only Josie looks in Josie's room. Finally, sometime in the wee hours of the morning, Josie takes Ruby’s body in a stolen car and burns it in a quarry. So: two dead girls, one identified by Josie as Ruby, the other identified as the missing Girl Guide.

But, something unexpected happens! Basil Blake arrives home at his cottage and discovers the body of the girl, and in a panic and somewhat drunk, takes the body to Colonel Bantry’s house and leaves it in his library! Miss Marple recognizes that the body in the Bantry’s library was probably not the intention, and this gives her the clue that Basil Blake was being framed.

Miss Marple immediately realizes that the burned body at the quarry and the missing Girl Guide are related to the death of Ruby Keene. When she discovers a record of Mark and Josie’s marriage, she knows just what happened. She sets a trap for the killers, by having Jeff announce that he will give his fortune to a charity for dancing girls, in Ruby’s memory. Desperate to keep from losing Jeff’s fortune, Mark and Josie try to murder Jeff before he can change his will—and they are caught in the act.

I’ll try to keep this part free from my dislike of Miss Marple. I think it’s a good mystery, with a complex plot. Like a lot of Christie’s mysteries, everything hinges on one piece of information—as soon as you know Mark and Josie are a couple, you realize that they could have worked together to do the murder. I also like that Mark’s big mouth is partially what leads Miss Marple to the solution; he talks about Ruby as having "teeth running all down her throat," but the girl in the Bantry’s library had buck teeth. So maybe they aren’t the same girl. But her cousin said the body was Ruby’s ... so the cousin must be in on it!

The clues are there. If you’re a Miss Marple fan, her little insights and village parallels are there, too. And—something unusual—there aren’t other, unrelated crimes that fog up the real crime. In other words, the whole story is just what happened, concerning the murder of Ruby Keene. But damned if I solved it! I didn’t get the gist until Miss Marple told the whole story in the last chapter. Which in a way, makes it a good mystery.