Jon spun, grappling the man's arms before the sword had time to swing, and ran the sharp edge of his rapier from hilt to tip across the man's throat.
The man grabbed Jon's rapier and cut him back. 
mnli hypothesis: The man grabbed Jon's rapier and cut him back.  premise: Jon spun, grappling the man's arms before the sword had time to swing, and ran the sharp edge of his rapier from hilt to tip across the man's throat.