Possible Clues:

• Chap coming a little late for Chesterton's Gabriel Syme?
• After a departure, many afraid to turn for help
• Aid surprisingly enlisted by Cook on an island, or by a castaway
• Assistant to Robinson Crusoe
• Servant whose name comes from "Robinson Crusoe"
• Assistant named for a Defoe character
• Islander giving way to woman on Saturday?
• For the crew, so, by the sound of it, he had his day