Jack knife

For Inspector Jonas Robb each night brings a new victim. One night also brings two strangers, David Elliot and Sara Grant, who appear to have no past. What they do have is knowledge about the elusive Whitechapel fiend, including the name he calls himself: Jack the Ripper. Because David and Sara do have a past, it just happens to be in the future. Sent back in time, they're in pursuit of a twenty-first century madman whose purpose is to change history. As the body count rises, Sara and David realize that their quarry and Robb's have become linked in a way that threatens not only Victorian London, but the very fabric of time.