I'll start the guide with the final map of the locations so that if you're missing just a few of them you won't have to read the whole guide.

In this side quest all you have to do is find him in his location and scan the symbol he leaves behind.

There are 4 locations you need to find him.

NOTE: He won't appear in the next location if you don't quit the map, you can do this by quitting the game or just getting inside a building.

In this one he's on the top of the ferris wheel, again just go talk to him and scan the symbol.

After you scan the symbol in the fourth location you'll automatically be taken to the batcomputer to solve the symbols puzzle.



It's a very simple one, just zoom and rotate the sigil until the four points matches the four locations you found him. It'll give a fifth location to go.





Going there you'll have a little talk with the watcher and it'll finish the mission.