This side-mission will actually being early on during the campaign during a sequence in which you need to track a van with the help of Nightwing, infiltrate a warehouse and destroy a weapons cache (which is why we’ll start this walkthrough at Cache number 2!). There are an additional four parts to this side-mission that can be undertaken at any point afterwards and will become playable once Nightwing updates you with additional weapon van locations.
After receiving intel from Nightwing, you can begin this part of the side-mission via the objective marker that appears. Approach the van. Pull out your Disruptor to plant a tracking device on the vehicle and then interact with the door. This will trigger a short scene after which the van will take off.
You’ll need to follow the vehicle a short distance through the city whilst staying out of sight. To do this, you’ll need to grapple up to the top of buildings and either grapple between them or practice using your grapnel Boost and glide combination. Either way, you’ll need to maintain your position high above whilst following the vehicle.
Eventually the vehicle will lead you across Founders’ Isle to the Sionis Industries warehouse on Bleake Island.
When you arrive at the warehouse, approach the front door and proceed inside. Take cover behind the first wall ahead and peek around the corner to spot a pair of Sentry Turrets – we can’t go in there just yet. Instead, look on the wall opposite the hallway we are in to see a control panel use the Remote Hacking Device to open the door next to it.
Switch to Remote Batmobile Control and drive it up to the now open door. Shoot the pair of Sentry Turrets inside. We can now move into the room as Batman. Enter the open elevator shaft to the left and grapple to the top. In the room up here interact with the fuse box to open the rooftop panels.
Exit the building and head up to the roof to find a series of skylights up here. Now that the shutters are open, we are able to break the glass here and proceed inside.
There are a large number of enemies in here with the group consisting of 20 Soldiers (two of whom have guns) and a Brute. The good news is that once you start the fight, Nightwing, who is also in the neighbourhood will also stop by to help you out. There are numerous environmental takedown objects around the room and the dual takedowns should be used whenever your combo meter is full enough to utilise them.
After the fight, enter the vault and use our Explosive Gel to tag one of the weapon crates. Once that is done, exit the vault and interact with the door to move it into place. Back off to a safe distance before detonating the Explosive Gel to destroy the cache to the max!
Note: For destroying the second weapon cache, on the Xbox One you’ll earn the achievement ‘Beautiful Boy’ . Note that the PlayStation 4 version will not give you a trophy at this point.