The Case of the Blonde Bonanza: Perry Mason Series, Book 67 (Unabridged‪)‬

Mason gives Della Street two weeks' vacation! That is, it was supposed to be a vacation, but Della turned it into a busman's holiday.

Target of interest was a well-stacked blonde - one who incredibly stashed away five enormous meals a day. Her name was Dianne, and when Mason unexpectedly appeared, he and Della discovered she had signed a contract to gain weight quickly in order to model clothes for "stylish stouts." Perry smelled a rat, and when he read the contract he found a nest of them. One led straight to murder....