Kill 4 enemies in the Tower Plaza with stealth kills

After you have found Cable and the "fangirl" you will arrive to the Tower Plaza, this is where you have to make 4 consecutive stealth kills, the first one i right in front of you, the second one is over at the broken walkway, wait for him to go into the bridge then go for the stealth kill, the third one is back at the broken walkway, and to the right, tha last one is right under you.