A secret apparatus that controls bombs by remote control is stolen from a laboratory. A federal agent is assigned to recover it, and his investigation leads him to a creepy mansion that is honeycombed with secret passage ways.
A man who's a dead ringer for the leader of an outlaw gang kills the gang leader, then takes his place to try to bring the gang to justice.
Bill Carson assumes the identity of gang leader Trigger Mallory in order to fool his gang and his girlfriend.
Fighter "Scotty" McQuade, contender for the light-heavyweight championship of the Pacific Coast,after being duped by his manager Ted Todd and fight-promoter Lew Slater, is disgusted with the fight game and decides to go back to punching cattle. He gets a job on the ranch owned by Colonel Hayden, where he once again encounters Slater, who has a crooked deal going that will cause Hayden to lose his ranch. With the aid of the Colonel's daughter, Betty Rose, and his pal "Frozen-Face" Cohen, McQuade breaks jail on a framed charge and puts an end to Slater's crooked dealings.
A government agent sets out to capture a gang of airmail bandits who use a death ray to blow planes out of the sky.
Lightning Carson's nephew has been falsely accused of murder. To get in with the gang, Lightning poses as a Mexican. He also appears as himself making his costume changes at his sister's ranch. Just as he about to bring in the gang, a henchman finds evidence of his masquerade and arrives to expose the hoax.
Martin Granville Jr., a star track-and-field athlete, has intentions of going to Claxton College, but changes his mind when he meets Pat Meredith, a co-ed at a rival college, changes his mind team and goes to college there, just as his father Martin Granville Sr., an alum of the school, had wished. But his father has ordered him not to play football. "Dad" Granville, has offered a $100,000 endowment to his old school, not knowing his son has joined the football team, but is going to withdraw it if his son plays in the Big Game against Claxton.
Ted Clark rescues pickpoket Danny from a mob, and restores Danny's loot, a pocketbook, to its owner Ann Dawson. She is carrying a letter that proves her brother, who is on death row, is innocent and Jim Grant is the guilty party. Ted and Danny help her escape from Grant's henchmen. They have several narrow escapes while on their way to give the proof to the Governor.
Cattlemen's Protective Association agent Tom Wade masquerades as outlaw Luke Bardes, hired to help Jed Travis persuade his niece Jennifer to sell him her ranch at a ridiculously low price, enabling him to turn a huge profit when the railroad has to buy the right-of-way through his property. Tom finds himself in big trouble when Bardes breaks out of jail and shows up at the ranch with a few of his rough-and-trouble companions.
A mysterious killer known as The Fiend uses an unusual bullet as his trademark for his murders.
A lawman poses as an outlaw, steals $10,000 from a cattle thief, then promises to return the money if he can join the gang--while finding a way to expose them.
Captain Matthews is paid 40,000 dollars in cash by Nick Conrad for his shipment of silk from China. About 15 seconds after he gets the cash, he's lured away on a false pretence and robbed by Conrad's henchmen. Newspaper reporter Jerry Mason witnesses the robbery and steals the cash from Conrad.
College student Jimmy Shaw inherits a racehorse, named Lightning Lad, and sells stock to fellow students in order to obtain funds for racing the horse. Lightning Lad wins very race he is entered in. Marion Braddock, a spoiled rich girl who owns a racing stable offers to buy Lightning Lad, but Jimmy refuses to sell. The day of the big handicap-race arrives and Jimmy and his fellow stockholders are on their way to the track. But a group of gamblers, betting on Lightning Lad to lose, have some skullduggery plans to ensure Lightning Lad does not win the race.
El Puma, a Mexican desert guide, escorts an archaeological expedition headed by Professor Lucius Lloyd through the Indian badlands of Mexico. Marian, the professor's niece accompanies the party as only she can translate the Aztec writings in the diary of her father, murdered on a similar expedition six years previous. The professor is murdered by a knife, and the weapon is recognized as the property of El Puma. Magpie, a Federal Investigator, knows that El Puma is really "Lightnin' Bill' Carson, a former federal agent who has been missing since Marian's father was slain. The reluctant Magpie believes that his old pal is guilty. Carson sets out to prove otherwise.
Madcap society girl June Bolton has a talent for trouble. Trying to evade a subpoena in connection with one of her misadventures, she winds up in jail and has to be bailed out by the family attorney, Dick Clayton. But June is soon in trouble again, this time involved with a mob boss and a shady lady. Exasperated by his wealthy client's reckless escapades, Clayton determines to quit... until he realizes he has fallen in love with the little madcap.
Chasing jewel thieves, Captain Carson and Magpie head for the border where Carson, posing as a Chinaman, opens a store that buys jewelry. To flush the thieves into the open, Carson wins all their money at poker. They agree to sell him the jewels but plan to kill him and keep both the jewels and the money.
Marshal and his men disguise themselves as gypsies to catch a gang of cattle thieves.
A man has died leaving a fortune somewhere on his ranch. Brandon and his cohorts think a map is hidden in a picture frame. But when they bid on the picture at the auction, newcomer Jerry Lane outbids them. He also buys the ranch so they place their housekeeper there to get the picture. And then to keep Jerry out of the way, they frame him for murder.
Cattlemen's Protective Association agent Tom Wade and his partner Happy are assigned to look into the disappearance of rancher John Carroll, who has been abducted by Carson, who wants to use his out-of-the-way ranch as a base for his smuggling operations. Complications arise as Carrol's daughter, Rita, looking for him, has an unfriendly run-in with Wade, then later is herself kidnapped by Carson.
Lightning Bill Carson and sidekick Magpie are after Burrows, the man that killed a friend of theirs. Burrows is after the Arden ranch and his gang are rustling their cattle. Bill is robbing Burrows while posing as the mysterious Phantom and it's not long before the two collide.
