You have pursued a mysterious figure dressed in Faramir's cloak ever since you saw it exiting the tunnels under Osgiliath. Is it truly Faramir? You will never know unless you catch up with it.
The mysterious figure remains ever one step ahead... and any hope of finding Faramir at last with it.
The mysterious figure has been revealed to be the Ranger Lúmithil, stabbed with a Morgul-blade and changed into a Cargûl.