A timeless spirit moves from host to host demanding vengeance for the innocent who are killed. The only problem is that wasn't it's true purpose.
A non-corporeal spirit - a Purpose - gives great power to it's host and compels them to seek out the guilty. The current host finds his world upended with no explanation by a young homeless man who dredges memories of his life before the Purpose took over. Memories he spent decades locking away.