Grant, police reporter on the New York Chronicle, is out on Long Island hunting quail, when his curiosity is aroused by the furtiveness of three armed men led by a woman on horseback who are conveying a covered load of something by motor truck along a deserted road he happens to cross. His curiosity leads him to investigate. The trail leads to an abandoned house. Grant sees barrel after barrel of gasoline stored in the cellar of this mysterious looking house. After the truck leaves he investigates and has a pitched battle with a wireless operator he surprises at work on the top floor. The operator presses a button thereby precipitating Grant into the basement. Breaking his bonds he again surprises the secret operator and in a struggle on the roof top Grant throws his adversary over and sits down at the wireless mechanism to unravel the mystery. He manages to pick up a message that astonishes him. He is in communication with a submarine lying on the bottom of the nearby harbor that expects to take on a supply of gasoline and oil, an act that a neutral country cannot tolerate. Meantime Nina, the girl spy in the employ of the foreign government, has summoned the submarine crew by wig wag signals. Grant manages to call the Brooklyn Navy yard before the raider’s crew arrives. Then begins a fight; in and out of windows, across slippery roof tops, the chase takes the reporter, culminating in his daring leap for the wireless frame. Uncoupling the crosspiece he swings down and out, describing a huge circle through the air until the momentum of his swing enables him to hook his legs around the limb of a tree on the opposite side of the yard. Scrambling to the ground he captures his prisoners just as the marines from the navy yard rush up.