You can't really have a story involving supernatural phenomena without having a healthy dose of fear mixed in. We fear the unknown, after all, because if we aren't familiar with it we can't know what it's capable of—and that's terrifying. So for our little boy in The Ocean at the End of the Lane, even though he has normal seven-year-old fears like being afraid of the dark, or making his father mad, he also has to look out for a vindictive flea and hunger birds that want to devour his heart.
While we gain insight into his character when we see how he handles these fears, we also learn to see the other side of the coin: monsters are far less terrifying when you can understand that they might be acting out of fear too.
Questions About Fear
According to Lettie, is Ursula Monkton a monster?
Why is the boy so scared of his father's anger?
After everything he's been through, at the end of the book is he still scared of the dark?
Why isn't everyone else afraid of Ursula Monkton?
Chew on This
Monsters may be creatures that are simply acting in response to their fears, and are therefore pitiable, but they are monsters because of how they do so.
Ursula Monkton is motivated by fear rather than a desire to spread happiness.