HMS Surprise is ordered to aid the Greek defenders of Missolonghi, the town having endured a prolonged Turk siege but about to fall as the garrison runs out of powder and the starving citizens have nothing but seaweed to eat.
Captain Patrick O'Connor strives to rescue his marooned shipmates, including his two closest friends in all the world, from certain death in the town as the final days of fighting approach a violent end, but finds himself pursued by three Turkish frigates in a protracted chase across the Ionian Sea through fierce storms, culminating in a spectacular battle.
Simon Ferguson, ship's surgeon, and Michael Marston, ship's chaplain, are overwhelmed by the casualties in the town and reduced to bleak despair by distressing events.
After three years of constant, bloody engagements and the death of many comrades, the toll is bearing down hard on the exhausted crew of the barky, and intolerable stresses afflict the minds of weary men who come to realise that they have given their utmost but can endure no longer.