The cover for my copy of Margaret Millar's The Listening Walls (1959) might not be as great as the cover for Beast in View (which was the cover that inspired me to pick the both of them up at a garage sale), but this is another very strong mystery novel with Millar's same focus on characterization, psychology, and suspense.
In this book, two best friends, Amy and Wilma, go off to Mexico on a vacation away from their husbands. Amy has always been the quiet one who aims to please, while Wilma is brash, loud, sometimes depressed, and often drunk. When Wilma buys an expensive silver box with Amy's husband's initials on it, the two of them have a fight over what that implies, then drink way too much tequila with an American gigolo in the bar. After they go back up to the room, Wilma jumps (or falls? or is pushed?) off the balcony and dies. While plenty of people on the busy street saw her land, no one saw or heard what happened in the hotel room except Amy and Consuela, the maid who often rests in the broom closet and curses her dumb boss and her flighty American boyfriend while listening to the guests through the thin hotel walls.
After Amy's husband, Rupert, brings her home from Mexico, he calls her overly-protective brother, Gill, and tells him that Amy decided to go away for awhile and wouldn't tell anyone where she was going. Gill doesn't really buy this, and when Rupert starts acting nervous, Gill hires a private detective to look into Amy's disappearance. What he finds is that Rupert is entangled in a trickier situation than anyone would have imagined...
Although the ending is a little stiff and the final twist pretty goofy, this is still a great book. More than the plot and the mystery, the characters -- particularly the supporting cast of secretaries, bartenders, and wives -- are what make this book stand apart from other perfectly fine mystery novels and make it something with a little more to bite into.