Completing the Line of Duty side quest in Batman: Arkham Knight requires tracking down missing crew members across Gotham's three main regions. Founders Island serves as the final and most heavily guarded sector where players must locate hostage firefighters held by armed militia groups. Knowing where each hostage is hidden ensures you can clear the quest efficiently and safely lock up Chief Underhill at GCPD HQ.

Finding the Northern Coast and Docks Crew

The northern side of Founders Island features several industrial complexes where crew members are being held under heavy guard. One firefighter is located at the middle of the northernmost port dock in Port Adams. Eliminating the sniper and taking out the local signal jammer makes clearing this encounter much easier.

Another crew member can be spotted in the northern dock area guarded by militia forces. You should use your detective vision while gliding over the northern shoreline to pinpoint their exact positions. Initiating combat from above allows you to take down key threats before the rest of the group reacts.

Navigating the Ryker Heights Underground Rescue

One of the trickiest hostages on Founders Island is hidden deep beneath the streets in the Ryker Heights district. To reach this location, you must search near the eastern side of the marked building for an open manhole cover. Dropping down into this tunnel reveals a heavy wall that blocks further progress into the underground chamber.

You will need to call in the Batmobile and use its power winch to pull down the reinforced structure. Once the barrier is destroyed, step through the doorway to face a large group of armed thugs. Using gadgets like the Disruptor on weapon crates before attacking prevents enemies from gaining a firepower advantage.

Rescuing Hostages Near Key Landmarks

Additional firefighters on Founders Island are stationed near prominent urban structures and shipping facilities. Exploring the western shoreline and construction zones will reveal small squads holding hostages captive. Watching for local surveillance chatter in the user interface helps confirm when you are near a hostage squad.

Approaching these locations requires tactical preparation due to sentry guns and armored enemies. Using environmental takedowns and fear multi-takedowns lets you neutralize multiple armed foes instantly. Clearing these areas guarantees that every standard crew member on the island is restored to safety.

Unlocking and Saving Chief Underhill

After saving all fifteen crew members across Gotham, the final objective directs you to the location of Fire Chief Underhill. He is held captive on a high rooftop in the northern district of Founders Island. This final encounter functions as a full predator scenario against sixteen heavily armed militia soldiers.

You can utilize floor grates, breakable walls, and generator traps to silently thin out the enemy ranks. Once all enemies are subdued, unbind Chief Underhill and drive him back to GCPD to complete the mission. Completing this objective grants WayneTech points and secures an official entry in your character showcase.