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.
Jon cut the man's throat with his rapier. 
mnli hypothesis: Jon cut the man's throat with his rapier.  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.