There is some kind of ninja in arkham who's watching you, you must find him, after you talk to him, he will disappear, leaving a symbol on the floor scan all four symbols, after this you map will show up, showing some kind of enigma, revealing he's 5th last location.
ATTENTION!!!
When you find him, you can do the Catch trphy,
you only have five attempts in one playthroughs, if have already finish this side mission you must start a new game.