Wealthy businessman Yoshitaka Mashiba tells his wife Ayane that he's divorcing her because she hasn't become pregnant. He reminds Ayane this was the deal when they married - a baby on the way within a year or he looks for someone new. Meanwhile Yoshitaka has been having an affair with Hiromi, Ayane's apprentice in the art of quilt making.
Heartbroken, Ayane goes off for the weekend to visit her parents. While she's away Yoshitaka is murdered with arsenic-laced coffee. The police suspect Ayane, but she has an ironclad alibi. To add to their problems, the police can't figure out how the arsenic got into the coffee.
Detective Kusanagi and his team question Yoshitaka's friends and acquaintances but have trouble advancing the case. So the female detective on the team, Kaoru Utsumi, consults the brilliant physicist Yukawa, who's a whiz at solving difficult cases.
Eventually the ingenious murder method and the killer are uncovered. To me the resolution was not very believable or satisfying. All in all I thought the book read like a typical cozy, but I would have liked the characters to be more fully developed and more interesting.