The Impossible Thing by Belinda Bauer

1926. On the towering cliffs of Yorkshire, men are lowered on ropes to steal the eggs of the sea birds who nest there. The most beautiful are sold for large sums. But when small and hungry Celie Sheppard finds an 'impossible' red egg, it will forever alter the course of her life - and the lives of others. One hundred years later in a remote cottage in Wales, Patrick Fort discovers his friend, Nick, and his mother tied up and robbed. The only thing missing: a carved case containing an incredible scarlet egg. Doggedly attempting to retrieve it, Patrick and Nick discover the cruel world of egg trafficking, and soon find themselves on the trail of a priceless collection of eggs lost to history. Until now.