Meet up with Nightwing at the marker and he'll give you a new gadget, the Disruptor. This lets you sabotage enemy weapons and weapon caches so they can't use them, but you can only get three at once. Test it out on the enemies below by shooting the two weapons, then the crate itself. Once you do that, go on and introduce yourself, as well as your fists, to them, being careful of the Brute.
After finishing off everyone, go up to the van and tag it using the Disruptor, then politely knock on the door to scare the goons into taking off. You'll have to follow them via the rooftops, so keep grappling across the city while keeping them relatively close. Eventually, they'll lead you back to their hideout, where you'll have to take down a total of six armed thugs. Be careful of the two sentry guns placed around the grounds.
Once they're all downed, head through the front door by the van and through the door on the ground. You will see a bunch of unarmed thugs down below, as well as the Penguin. Slide down the chute you find and go to the grate cover, popping out to interrogate the Penguin. Keep an eye out on the screen, as some thugs will try to attack you while you're holding the Penguin, so counter them when the prompt appears.
Eventually, two thugs manage to get a hold on you, but a certain friend shows up to help you out. As with the fight earlier with Catwoman, you can switch to Nightwing at any time with L1, as well as dual team takedown when you see the prompt. In fact, it's pretty easy to defeat all of these enemies with Nightwing, as he is quite fast with his attacks, but you don't need to do that if you don't want.
When you're finished, Batman mentions that this weapon cache needs to go, so head through the door and spray some Explosive Gel on the marked location. As soon as you do, leave and close the vault door, then walk away far enough until you can detonate the gel, blowing up the weapons cache. Leave the building and get ready to go to Founders' Island, except you'll be ambushed as soon as you get outside.
As soon as you see the prompt to grapple to the beam above you, do it and they'll open fire. There's nothing you can do as Batman, but you can switch to the Batmobile. Drive up to the top of the parking lot that is shown to you and use the Batmobile's weapons to take out all of the enemies and the two sentry guns. Leave and go to Founders' Island for the next story portion.
