Stripped of his private detective licence and devastated by the murder of his partner Lily Truscott, Cliff Hardy travels to the US to help Lily's brother's tilt for a world boxing title. In San Diego he suffers a heart attack and undergoes a quadruple bypass. He meets nurse Margaret McKinley, an expatriate Australian who is concerned about the disappearance in Sydney of her father - renowned geologist Dr Henry McKinley.
Hardy undertakes to investigate in association with Hank Bachelor, his former associate who now runs his own agency. It turns out that McKinley had discovered a way to tap into the massive Sydney basin acquifier, a possible solution to the city's water problems. Working with Margaret who visits Sydney, Bachelor, and his daughter, Megan, Hardy confronts an old enemy and contending forces bent on exploiting the discovery and prepared to kill for it.
Energised by the case and by his attachment to Margaret, Hardy obeys the strict rules for the restoration of his health - but in pursuing the truth and the malefactors, he makes his own rules.