Synopsis: When a little dog appears at a family picnic, the girl and boy play with him all afternoon, and they name him Willy. At day's end they say good-bye. But the dog has won their hearts and stays on their minds.The following Saturday the family returns to the picnic grounds to look for Willy, but they are not alone -- the dogcatcher is looking for him, too...Caldecott Medalist Marc Simont's heartwarming tale of a stray dog who finds a home is told…