Bringing Down the Wall — David P. Reiter

Joshua misses his grandpa, but his mother has told him he's not allowed to see him. She won't explain why, but Joshua suspects it has something to do with his grandpa's new wife, Riva. One day, Joshua sets out on his own to visit his grandpa and Riva to discover the truth. He hopes he can find a way to make it up between them and his mother. But will he be able to bring down the wall guarding their secrets?