Deathworld centers on Jason dinAlt, a professional gambler who uses his erratic psionic abilities to tip the odds in his favor. While visiting the planet Cassylia, he is challenged by a man named Kerk Pyrrus (an ambassador of the planet Pyrrus) to turn a large amount of money into an immense sum by gambling at a government-run casino. He succeeds and survives the planetary government's desperate efforts to take back the money. Bothered that he may finally have met someone superior to him, he decides to accompany Kerk to Pyrrus, despite being warned that it is the deadliest world ever colonized by humans.