Each car on the train has one more zoo animal than the one before, from the first car with an elephant to the last with ten birds.

"Ducks overboard!" shouts the captain, as a giant wave washes a box of 10 little rubber ducks off his cargo ship and into the sea. One drifts west, where a friendly dolphin jumps over it. A whale sings to another. But as the sun sets, the 10th little rubber duck is left all alone, bobbing helplessly on the big wide sea. Following the little ducks as they float to all parts of the globe, young explorers can see for themselves the meanings of directional...