When Doc Ford investigates a tragedy that claims the life of his close friend, diver Janet Mueller, he uncovers dark rumors about the case involving everything from fraud to smuggling to murder.

Trapped underwater when a cave collapses in the remote Florida lake they are exploring, Doc Ford escapes and begins a desperate effort to rescue his two companions when he is intercepted by a murderous pair of ex-cons who are searching for a sunken treasure.

When a local teen from a trailer park being targeted by powerful developers witnesses their hired gun committing a murder, her only hope for survival falls in the hands of Doc Ford and Tomlinson, who undertake a search through the underground in the hopes of finding her first.

"Marine biologist and former government agent Doc Ford is sure he's beyond the point of being surprised by his longtime pal Tomlinson's madcap tales of his misspent youth. But he's stunned anew when avowed bachelor Tomlinson reveals that as a younger man strapped for cash, he'd unwittingly fathered multiple children via for-profit sperm bank donations. Thanks to genealogy websites, Tomlinson's now-grown offspring have tracked him down, seeking answers...