The Clue of the Broken Locket is the 11th book in the Nancy Drew Mystery Stories series. The original edition, first published in 1934, was written by Mildred Benson, under the pseudonym Carolyn Keene. The revised version was published in 1965, and is a completely different story published under the same title.

Plot summary

The 1934 text primarily deals with an adoption of 18 month old twins, and reuniting of two different families. Carson Drew handles an adoption for the wealthy showbiz couple, Johnny and Kitty Blair. The Blairs invite Nancy and friend Bess Marvin to a celebration, where the Blairs and other guests are distracted by heavy drinking and smoking. Nancy manages to steal some articles found with the abandoned babies, clothing and the mysterious broken half of a locket. Nancy tries to aid the incompetent maid in caring for the children. The maid is fired as a result, and with her boyfriend, plants stolen jewellery in Nancy's car as revenge. Nancy tries to help the Blairs' butler Rodney, and a nurse, Ruth Brown, who it turns out are long-separated twins themselves. Nancy must discover the whereabouts of the twins' missing natural parents, encountering resistance from the spendthrift, and near bankrupt Blairs. The cover art for the original dust jacket is uncredited. Russell Tandy drew the frontispiece and original three internal illustrations for the volume, in 1934. A facsimile of this edition is available from Applewood Books. In 1950, the cover art was modernized by Bill Gillies. In 1962, the cover art was modernized again, by Rudy Nappi.

The revised version of the story was published in 1965. In it, Nancy travels to Maryland and is bewildered by an odd haunting at a lake where she is staying. A phantom of an old excursion launch, which sank at the turn of the century, keeps appearing. Nancy is further perplexed by the fact that hostess Cecily (who has a "Broken Locket" to a fortune) appears to have a twin in the vicinity. Cecily's boyfriend, a rock star, is experiencing trouble with pirated records, and Nancy takes on investigation of this mystery as well. Another angle involves Pudding Stone Lodge, a stone mansion on the lake, where odd activities are observed. The exciting solution is revealed by the clue in the locket. Rudy Nappi illustrated the cover of the 1965 text.