Neil McCallum breaks his brother, Aldo Ray, and three others out of prison. Ray wants a retrial, and talks about getting the public on his side, while the others just want away, but go along, with grumbling. But the boat they are on wrecks its piston, and they put up at Fort Denison in Sidney Harbor, aka, Pinchgut Island. They take the keeper, his wife and daughter hostage, and plan to get away the following evening, after the tourists have left. But that goes wrong, too, and they come up with a third plan: there are shells inside the disused fort, and a working gun, and a ship in the harbor with 15,000 tons of explosives. A shell in that ship will destroy miles and miles of Sidney. The authorities are paralyzed. They could destroy everyone in the fort, but then what would public opinion say about the keeper and his family? The only man who can order a retrial for Ray is out of town and refuses to act.
The last movie produced by Ealing Studios under Michael Balcon is in no wise a comedy, although there are some funny bits as the harbor area is evacuated. Instead, it's about the men under pressure, the authorities who refuse to budge because of red tape and conviction, and the increasingly frenzied behavior of Ray, as his brother expresses doubts.
Director Harry Watt had become a director in the GPO unit under Humphrey Jennings. He directed the fine NIGHT MAIL, and did uncredited direction on LONDON CAN TAKE IT. During the War he moved to Ealing. After the War he directed their overseas movies. After this, he went to TV and eventually back into documentary work. He died in 1987 at the age of 80.