A Navy commander fights to prove the battle-worthiness of the PT boat at the start of World War II.

In 1941, the 3rd Motor Torpedo Boat Squadron of the U.S. Navy is sent to Manila Bay to help defend the Philippine Islands against invasion by the Japanese army. The squadron, under the command of Lt. John Brickley, arrives at its island post only to be ridiculed by some of the top military leaders, who do not believe that the small torpedo boats can be effective. Brick, who is fiercely proud of his squadron, is angered by the insults and vows to prove his detractors wrong. His first opportunity to put the squadron to good use finally comes when news arrives that the Japanese have bombed Pearl Harbor. Though initially assigned to messenger duty, Brick's squadron is later pressed into combat duty when Japanese warplanes descend on the island in a surprise attack. The torpedo squadron shoots down three of the Japanese planes, but the Japanese succeed in destroying much of the base, which is later ordered closed by Admiral Blackwell. Brick's squadron is then sent to Sisiman Cove, on the island of Bataan, to run a messenger service. The new assignment infuriates one of Brick's men, Lt. "Rusty" Ryan, who is eager to be involved in serious combat and has repeatedly asked Brick to be reassigned to a destroyer. When Blackwell assigns the 3rd Squadron to send two boats to sink a Japanese cruiser that is shelling positions at Bataan, Brick chooses his boat and Rusty's for the job. Just as they are about to ship out, though, Brick notices a cut on Rusty's arm and sends him to a military hospital for treatment. There, Rusty is diagnosed with blood poisoning and placed under the care of nurse Lt. Sandy Davyss. While Rusty awaits surgery at the hospital, Brick's boats destroy the Japanese cruiser. Rusty pursues a romance with Sandy after his operation, but their romance is cut short when Brick orders Rusty to return to the squadron. The torpedo squadron's attacks against the Japanese forces continue with great success, though Brick loses some of his men and boats in combat. One day, Brick and Rusty are assigned the important task of transporting Admiral Blackwell and General Douglas MacArthur to the island of Mindanao. Before embarking on the dangerous journey, Rusty telephones Sandy to bid her what may be a final farewell. When only three of the four boats in Brick's squadron arrive at their destination, Brick sends out a search party for the missing boat. It is eventually found, but because it has suffered serious damage, it is taken out of service. Brick's force is now reduced to only two boats, his and Rusty's. Brick is assigned his most challenging mission yet when he is ordered to destroy a Japanese cruiser headed toward Corregidor. The two torpedo boats encounter a barrage of enemy fire at sea, but succeed in destroying their target. Though both boats survive the mission, Rusty's boat is later destroyed in an aerial attack. When news arrives that 36,000 American soldiers have surrendered at Bataan, and that the Japanese are now battling at Corregidor, the last American strong point in the Philippines, Rusty and Brick are given orders to leave their squadron and go to Australia to train a new torpedo boat force. Despite promises by the Army that they will be returned to the Philippines with a stronger force to fight the Japanese, Brick and Rusty refuse the reassignment and try to stay on the island with the rest of their squadron. Their attempt to stay fails, however, and they are flown out on the last plane leaving the Philippines, not knowing if they will ever see their squadron again.