My 4th grade teacher in 1958-59 read us a chapter-a-day in a children’s book about a group of kids trying to solve a mystery. While trailing a bunch of crooks, the smell of the kids’ mosquito spray (quinine) gave them away. Calpurnia was the housekeeper.
You may be thinking of the scene in Elizabeth Enright’s And Then There Were Five, when Rush and his friend Mark spy on some bootleggers. They are wearing citronella and somebody smells it, so they have to make a run for it. The housekeeper in that book is Cuffy.
Calpurnia is the housekeeper in To Kill a Mockingbird, unless there’s another Calpurnia somewhere.
Correction to previous post: should just be Then There Were Five, not And Then.
I remember a mystery by Margaret Goff Clark with a similar plotline. I can’t remember which one though.