Who were the characters that the plan depended on? Why

James jumps to action and orders Silkworm to begin spinning, even though she is tired; he then takes Silkworm's rope and leaps down to rescue Centipede.

Before he leaves the peach, James instructs his friends to begin pulling on the rope when they feel three tugs. Soon James is gone, and the others believe that both James and the Centipede have been lost forever, when suddenly they feel three tugs and pull the two of them up. They are both soaking wet, and Centipede tells everyone that James swam around the ocean until he found and rescued him. Old-Green-Grasshopper informs the other passengers that the peach has continued to ascend, and Miss Spider suggests moving downstairs. Yet Old-Green-Grasshopper believes it would be best for everyone to stay up top and keep watch, and that is exactly what they decide to do.