Eustace finds himself in Narnia once again, along with a friend, Jill. The great lion, Aslan, assigns them a mission to find a lost prince. To guide them, he gives them four signs to remember and follow at all costs. As they begin, they meet an unlikely guide who lives in a marsh and helps them form a plan. However, Eustace and Jill’s lack of focus and forgetfulness puts them in grave danger.

After a brave escape, they find themselves in an underworld surrounded by earthmen. They are taken to a dark knight and an evil enchantress; their guide encourages them to remember and follow Aslan’s instructions, no matter the cost.