The story:
As the Walkers finally arrive on Eden (see S125 Phantom Head Peak), the Phantom and Rex discover an unconscious woman diver on the reef that separates the isle from the ocean.

Soon the girl can tell her rescuers about a recent diving session in which she and her instructor found a gold treasure on the seabed, leading to the girl being attacked and left for dead. With the trail going cold fast, the Phantom takes off in a bid to find the treasure and the murderer before it is too late...