Cornell University professor Arthur Maxon, who has been experimenting in the creation of artificial life, travels with his daughter Virginia to one of the remote Pamarung Islands in the East Indies to pursue his project. Their departure is noted with interest by a young man, Townsend J. Harper, Jr., who is quite taken with Virginia and determines to find out where they are going. In Singapore, Maxon commissions Dr. Carl von Horn to take them the remainder of the way to their destination in his yacht the Ithaca, and then to assist him in his experiments. On the island the group fights off a pirate attack and builds a fort. Maxon and von Horn begin their experiments, growing several living creatures in chemical vats, humanoid but mindless and ugly. Maxon hopes Experiment Number Thirteen will result in a perfect human being, and in his fanatic obsession plans to wed Virginia to this ultimate creation. Von Horn retains a more realistic viewpoint and hopes to marry her himself, leading to friction. Meanwhile, locals including Budadreen, one of von Horn's crewmen, and Muda Saffir, leader of the pirates, conspire against the scientists, who they believe are hiding treasure. They are watched closely by Chinese cook Sing Lee, who recognizes the pirate. Experiment Number Thirteen indeed appears to result in a physically perfect man, but as soon as the scientists discover this an emergency distracts them. Experiment Number One has escaped and abducted Virginia. Maxon, von Horn and Sing Lee pursue the monster, only to find it dead at the hands of Number Thirteen, also escaped from the lab in the wake of the scientists' departure. Thinking Virginia still in danger, von Horn attacks the creature and is nearly killed himself, but is spared by Thirteen when Virginia pleads for his life. Ignorant of the handsome stranger's origin, the girl finds herself attracted to him. Maxon and von Horn return Thirteen to the lab and begin educating him. Von Horn privately discloses to Virginia Maxon's plan to wed her to one of his creatures, while concealing it is her rescuer to whom she is to be wed. Separately, he informs Thirteen of his artificial origin. Both recipients of his confidences are horrified. Thirteen, or Jack, as he is now called, is convinced that he is a soulless monster and that Maxon must be stopped.