Michael Larson is a widower, an American dolphin researcher, who moves to Australia with his two young children and tries to build a new life.

Michael's old pal from graduate school comes for a visit. What Mike doesn't know is that Peter is a member of a radical group called Planetwatch and is in town as part of a revenge plot to plant a bomb on a yacht.

One of the dolphins, Delbert, swallows two firecrackers that were carelessly tossed at sea and is slowly poisoned.

Lisa Ruddick, a journalist. uses a story on Jonathan's research as a ruse to gather damaging information on Jonathan's boss, the eccentric Baron Trent.

Mike's experiments using sound waves with the dolphins is a breakthrough in communications, but his boss Trent sees it as his chance to go in search of sunken treasure off the coast.

Katie deals with an admirer, David deals with an adversary and Didge deals with a dilemma.

Didge welcomes two stranded fishermen, unaware that they are escaped convicts.

Larson's skeptical in-laws arrive for a visit, but when they see the kids are not too keen about their Australian environment, they decide to take them back to the States.