Dr Carl Maia leads an expedition to the jungles of the Amazon, where he uncovers a fossil, which on closer inspection is found to be a claw; with webbed fingers. Maia believes that this is the missing link between land and sea animals from the Devonian period. He returns to the US, where he visits his former student David Reed, who now works at an aquarium in California. David approaches his financially minded boss Mark Williams and persuades him to fund a return expedition to find the remainder of the skeleton.