Barrier of Tears - The Saga of Bob, #4

Bob has saved humanity throughout the galaxy on numerous occasions, and successfully battled against fearsome opponents. For his efforts, he was forced to be reborn as merely human. Despite his greatly diminished powers, a new challenge has been thrust upon him. An ancient refuge has been turned into a prison, and a force that once protected humanity is poised to destroy it. Once again, Bob must dive into mysteries that span the galaxy, uncovering and decoding clues.
Once again, he is opposed by secretive and powerful forces, some human and some not. The chances of success are low and his chances of survival even lower. There are many types of barriers, and Bob will discover that the least substantial can be the most deadly.