Purgatory key

the long version

After Lissa Rogers and Kendra Kozak set out on a summer adventure, the two teenagers arrive at Terrebonne Key, an island in the Louisiana bayou rumored to be the location of a legendary treasure. But they aren't alone on the island. Now dangerous fugitives are holding them hostage, and the girls' only hope for survival is investigator Del Shannon. When Del learns that Lissa is the granddaughter of her former mentor, Louise Lassiter, she decides to take the case. But then Del botches the ransom money drop, and her chances of rescuing Lissa and Kendra grow slim. With time running out, Del teams up with Frank Falconet, an old flame from her past, to find the two girls, and the secret to Terrebonne Key's hidden fortune, before it's too late.--From back book cover.