The Story of the Amulet - Edith Nesbit - Bog

While their mother and father are out of the country, Cyril, Anthea, Robert, Jane and the Lamb are staying with the "old nurse" in her boarding house. There is only one other boarder, an old Egyptoligist, whom the children soon befriend. When they rescue their old friend the Psammead from a pet shop, the grateful fairy leads them to half an amulet which has the power to take them back in time in search of the other half - and the complete amulet can give them their heart's desire! But magic can cause problems in real life, especially when the Queen of Babylon visits the children in London.