Produced and directed by Zoltan Korda with a screenplay by John Howard Lawson (Blockade (1938)) from an adaptation by Janet Stevenson and Philip Stevenson (Story of G.I. Joe (1945)) of Pobyeda a play by Ilya Vershinin and Mikhail Ruderman this psychological war drama features Paul Muni as Alexei Kulkov a Russian soldier who along with a female resistance fighter as his assistant Lisa Elenko (Marguerite Chapman) finds himself in a position to extract vital intelligence information from some Nazis that he’s taken prisoner while all are trapped in a bombed out building.
It’s 1942 and the Russians have been driven back such that the German front is a thousand miles into their own country. But Ostrovski (Ian Wolfe uncredited) and Colonel Seminov (George Macready) have a plan – to build an unseen bridge eighteen inches under the river which will enable Russian tanks and troops to cross – the first step of which is to drop paratroopers behind enemy lines. Among these are Kulkov his German Shepherd dog and Kirichenko (Larry Parks) who are led by Elenko once they land. They attack the German stronghold at a factory and the Russians win the battle until an alerted squadron of enemy planes bomb the facility trapping Kulkov and Elenko with seven German soldiers that they’d just discovered and captured. Fortunately Kulkov’s dog sniffed out this fact and using a kind of Morse code on a pipe that extends from the room to the surface Kirichenko learns the situation from his comrade and decides to venture back across the river to inform his commanding officers.
By flashlight lantern then even candlelight Kulkov and Elenko take turns keeping a machine gun trained on the Germans at the other end of the large room. Over the course of many hours Kulkov uses his cunning and reasoning abilities to learn that among his prisoners is a German officer who might have important information that will help his country’s counterattack. Of course the Nazis do their best to keep the identity of their officer a secret while they scheme to overcome the increasingly tired Kulkov and Elenko who is stabbed in a brief scuffle that ensues when the lantern is knocked out. As the hours become days through interrogation and tricks Kulkov learns the identity of the officer and then plays a dangerous game of “who knows what” during which he reveals more than he intended about the “invisible” bridge being built by his countrymen. When the trapped hear digging and voices on the surface they know that the end is near but it’s unclear who it is. Kulkov knows that he must kill his Nazi prisoners if it’s Germans who are about to rescue them but it turns out to be his Russian comrades dog and Col. Seminov who is thrilled to learn the location of his enemy’s concentration.