Then he rearranged his feathers, and dropped a rough brown pebble into her hand. ‘Thank you,’ said Winnet. ‘What is it?’ ‘It’s my heart.’ ‘But it’s made of stone.’ ‘I know,’ the raven replied sadly. ‘You see I chose to stay, oh, a long time ago, and my heart grew thick with sorrow, and finally set. It will remind you.’
sorrow turns heart to stone
pebble as a reminder (of what?)
