HMS Duncan has a long journey ahead of her as she receives orders to support a French aircraft carrier on campaign in the Middle East. A female lieutenant training to become captain is given full control of the warship for 24 hours.
HMS Duncan joins Operation Inherent Resolve, protecting a French Aircraft Carrier off the coast of Syria. The ship detects a Russian submarine and a mystery helicopter, then receives top secret orders to help evacuate 33 trapped Britons.
In a bid to bolster relations with NATO allies in the Black Sea, the crew have been sent to Ukraine. Captain Tom hosts the Ukrainian president, before new orders see the warship head to the Gulf.
H.M.S. Duncan is ordered to the Straits of Hormuz after Iranian forces take control of the British flagged tanker Stena Impero and hold the crew hostage.
While Iran still holds the Stena Impero, H.M.S. Duncan is ordered to continue escorting fuel tankers safely through the Strait of Hormuz. After completing her duties she returns home.