When Charlie visits his hardworking grandparents in the summer, he often is left to himself, and he is lonely. So he goes out to play by the stream, with a tin can for tadpoles, a special weed-whacking stick, and stones to drop from the iron bridge. One day he notices that when he strikes the bridge with a big stone, it rings with a bong like a church bell and echoes into the valley. And sometimes a faint, very distant, different-sounding bong comes back. Is it an echo of an echo? Or could someone else, like him, be ringing another bridge altogether?