In a quiet New England port town, a deep-rooted rivalry between two tugboat operators sets the stage for a larger war drama. Pop Thorson [Wallace Beery], a self-made, widowed boatman who built his own vessel and lives aboard it with his adult daughter Susan Thorson [Virginia Grey], clashes with Rocky Blake [Chester Morris], the disciplined rival who believes in playing by the rules. The feud isn’t just about bragging rights or contracts; it’s a clash of styles, pride, and stubborn dedication to family loyalties. Susan adores her father but also cares for Blake, which complicates the tensions between the men and keeps their squabbles from spilling into open bitterness.
With the United States entering World War I, the Navy begins recruiting for anti-submarine warfare. Susan and Pop use a clever ruse to push Blake into service by pretending that Pop is about to enlist, sparking a grudging respect between the two men as Blake rises in rank and responsibility. The maneuver pays off when Pop secures a coveted contract, and, as soon as his tug is back in service, it encounters a German submarine. The U-boat orders the crew into lifeboats and sinks the tug and its barge, a devastating blow that hardens the war’s reach into civilian life. The same German U-Boat Captain [Carl Esmond] leads the assault, signaling how the war’s shadow extends into everyday coastal life.
Thorson arrives in port and is promptly recruited into the Navy, earning the rank of ensign and a command in a small fleet of new sub chasers. His instinct and experience set him at odds with naval discipline, especially when his superior is Blake, now a lieutenant dedicated to duty. Blake’s measured approach clashes with Thorson’s bold, intuitive style, and the two men struggle to find common ground as they prepare for dangerous missions. Yet there is a strand of mutual respect: Blake recognizes Thorson’s hard-earned skill, and Thorson begins to see how strategic obedience can work alongside raw courage.
On their first mission, Thorson champions a risky but intuitive plan. He reasons that any submarine would avoid a storm-wracked area and would shelter in the lee of Nantucket Island. Despite orders, he steers toward that lee, and he does indeed locate the same German sub. The German captain foils the attack by releasing oil to disguise the submarine’s presence and sinks a lightship before slipping away. A damaged cable tangles in Thorson’s propeller, forcing him into the water to free it. Blake arrives just in time to rescue him, underscoring the fragile line between daring and danger—and the thin margin between success and disaster.
The aftermath is harsh. Thorson faces a court-martial for insubordination, is demoted to ordinary seaman, and sent to shore duty. With the war pressing forward, he considers desertion to Canada with Susan, but Blake intervenes, offering a path back into action. Thorson is reassigned to a daring new assignment: a decoy ship that looks like a civilian fishing schooner but hides a concealed radio to summon the sub chasers as needed. This clever ruse brings them into the sights of the same submarine, and the Germans board the decoy to uncover the radio. The pursuit intensifies as the decoy is attacked, and the German crew discovers the hidden radio. Undeterred, Blake’s fleet closes in, and Thorson orders the decoy to ram the submarine, risking everything to strike a decisive blow.
The submarine sinks the decoy and takes Thorson aboard as hostage, then dives to the seabed. In a tense, calculated moment, Thorson seizes a window of opportunity, locks himself in a room, and bangs on the hull with a wrench, signaling the listening sub chasers to the sub’s location. Blake recognizes that a direct, aggressive strike is the only way to end the standoff, even though it puts Thorson at great risk. The submarine is damaged but still capable of surfacing, and Thorson, along with the submarine’s crew, is ultimately rescued by the pursuing ships.
In the end, Thorson is awarded the Medal of Honor, restored to the rank of ensign, and given command of another sub chaser. The resolution brings a triumphant closure to a story defined by grit, loyalty, and the power of perseverance under pressure. The port’s residents, along with Susan, celebrate not only his return to duty but the resilience of a community united by war and the hope that a man’s courage can redeem a lifetime of stubborn striving.
