It's time to face up to Dawes on his island stronghold. This is how to take down the entire operation.
Battlefield Hardline guide: Episode 10 - Legacy
From the jetty head up the path to the first set of guards, who you can arrest easily. In the shed is a Tactical Gear box so arm your loadout. From there follow the path and climb up the watch tower to scan for guards. It's inevitable you're going to have to start shooting at some point, so you want to tag as many as possible.
Take down the guy with the open warrant using cuffs or the stun gun then pick off the rest of the goons. There are explosive barrels here that you can use to thin out the crowd, but if you set the alarm off expect a van load of enemies on top of the usual crew. If you want to avoid the fight you'll have to grab the evidence on the fax machine quietly.
From here go up the path and you can go left or right. Go left to the bungalows and main residence and you've got the option to change your equipment at the Tactical Gear box.
Carry on until you see the pool on your left, but move up the steps to the watch tower where you can again tag all the enemies around the pool, the evidence and a dude with an outstanding warrant. This is a big space so it's not too hard to take the majority of the enemies down here silently, using cuffs and the taser. There's plenty of cover around the outside of the pool, so you can distract guards using shell casings and sneak all the way to the back where the bar and dance floor is. You'll also find the evidence in the far right building.
Once you've dealt with everyone here, carry along the path and hang a right to the services area, where you'll see the final guy with the outstanding warrant next to two massive explosives. Take him down silently and decide if you want a firefight with these guys or grab the evidence silently - from the explosive tanks it's in the far east corner.
Now you've cleared up the three pockets of bad guys it's time to head back and up to the main mansion. You can sneak up to the grounds or you can find the motorbike and ride it over a ramp and pick up the Dare Devil achievement/trophy. We chose the latter because we felt like having some loud fun but there's a rock on the right of the entrance that you can climb over into the grounds if you want to be a bit more subtle.
If you're being sneaky you can arrest the guy in front of the main gates and the two fixing the car easily, then go left and around the wall to double back and arrest another three in front of the steps. If you now go to the right side of the mansion you can arrest another two guards just before you find an entrance to the mansion. Better still, go up all the steps in the outside where you'll find yourself on the roof. You can now tag enemies in the mansion through the skylight.
Whether you're shooting or sneaking you need to work your way into the mansion, down the stairs and through into the backyard, where you'll find a building with Dawes' office.
Once you've dealt with Dawes, check the note on his desk and pull the dragon on the bookshelf to open the passage. Open the vault and… you've completed Battlefield Hardline. Congratulations!