In Chapter 11 of "The Cay," there is a metaphor on a certain page (p. 81 of my edition). The page begins by discussing Phillip's growing...

In Chapter 11 of The Cay, Phillip and Timothy are stranded on the cay after the ship Phillip is traveling on is torpedoed. Phillip, who has lost his sight, has become dependent on Timothy, but Timothy also insists that Phillip become as independent as possible. To this end, Timothy makes Phillip a cane. Phillip also navigates around the island using "the vine rope," or the rope that Timothy has made for him. Phillip can use this vine rope to get to the beach on his own. If Timothy is fishing on the reef, Phillip can use the vine rope to get to the beach to light the fire if he hears a plane and wants to draw its attention. Phillip has a measure of independence by using this rope. 

Phillip says, "Our cay seemed a lovely island and I wished that I could see it. I planned to walk around it at least once a day, following the vine rope from the ridge to the beach" (page 80-81). He also says that he is becoming less dependent on the rope and on Timothy himself, so the vine rope is a metaphor. It is a symbol of the way in which Timothy has helped Phillip become more independent, as Phillip can use this rope to navigate by himself.

Later in this chapter, Timothy says the island has a jumbi, or evil spirit, and he thinks the cat might be the evil spirit. However, this is not a metaphor, or symbol. Instead, the idea of the evil spirit is foreshadowing or predicting the dangerous events that are to come later in the novel.