In the waning days of WWI, a U.S. "Mystery Ship," sets sail for the coast of Spain towing a submarine. Their mission is to find and sink a U-boat that has been especially effective in attacking Allied shipping. Posing as a harmless schooner, the mystery ship is in fact fitted with a formidable gun capable of sinking a U-boat. Stopping in the Canary Islands to refuel, the crew interacts with locals involved with Germans, and with Germans themselves, including the sister of the U-Boat commander, who is lurking offshore waiting for the coming battle.
Two young men, one rich, one middle class, both in love with the same woman, become US Air Corps fighter pilots and, eventually, heroic flying aces during World War I. Devoted best friends, their mutual love of the girl eventually threatens their bond. Meanwhile, a hometown girl who's the lovestruck lifelong next door neighbor of one of them pines away.
During America’s Civil War, Union spies steal engineer Johnny Gray's beloved locomotive, 'The General'—with Johnnie's lady love aboard an attached boxcar—and he single-handedly must do all in his power to both get The General back and to rescue Annabelle.
A nobleman vows to avenge the death of his father by the hands of pirates. To this end, he infiltrates the pirate band; Acting in character, he single-handedly captures a merchant vessel, but things are complicated when he finds that there is a beautiful young woman of royal blood aboard.
The wealthy and impulsive Rollo Treadway decides to propose to his beautiful socialite neighbor, Betsy O'Brien. Although Betsy turns Rollo down, he still opts to go on the cruise that he intended as their honeymoon. When circumstances find both Rollo and Betsy on the wrong ship, they end up having adventures on the high seas.
A film projectionist longs to be a detective, and puts his meagre skills to work when he is framed by a rival for stealing his girlfriend's father's pocketwatch.
A female ape takes to mothering the orphaned boy (Tarzan) and raises him over the course of many years until a rescue mission is finally launched and the search party combs the jungle for the long-time missing Lord Greystoke. But then, one of the search members, Jane Porter, gets separated from the group and comes face to face with fearsome wild animals. Tarzan saves her from harm just in the knick of time and love begins to blossom.