“Please - Aslan,” said Lucy, “Can anything be done to save Edmund?” 

“All shall be done,” said Aslan. “But it may be harder than you think.” 

And then he was silent again for some time. Up to that moment Lucy had been thinking how royal and strong and peaceful his face looked; now it suddenly came into her head that he looked sad as well. But next minute that expression was quite gone. The Lion shook his mane and clapped his paws together.

(The Chronicles of Narnia: The Lion, The Witch, and The Wardrobe).