When a treasure hunter seeks a downed airplane in the jungles of Africa, he encounters one of the passenger's young daughter, now fully grown, and with a gorilla protector.
Cosmo Jones, a correspondence-school detective from a small town, comes to the big city to offer his services to the police. He happens by where a gangster is killed by an opposing gang. Socialite Phyllis Blake is running around with gang member Tom and the opposing gang plan on kidnapping her. Cosmo is with Sergeant Flanagan when the attempt is made in front of a night club, where a bystander is seriously wounded in the gun-battle. Police Chief Murphy blames Flanagan for the shooting and demotes him. Cosmo, with the aid of a porter, Eustace and Flanagan's fiancée, Susan, tries to find the killer. Phyllis is finally kidnapped and Cosmo decides the act was committed by one of the two gangs. He has her father place an ad in the newspaper that contact has been made with the kidnappers. Each gang thinks the other is pulling a double cross, and one gang wipes out the other.
In the midst of World War II, Sherlock Holmes rescues the Swiss inventor of a new bomb-sight from the Gestapo and brings him to England, where he quickly falls into the clutches of the evil Professor Moriarty.
It is prior to the commencement of World War II, and Japan's fiendish Black Dragon Society is hatching an evil plot with the Nazis. They instruct a brilliant scientist, Dr. Melcher, to travel to Japan on a secret mission. There he operates on six Japanese conspirators, transforming them to resemble six American leaders. The actual leaders are murdered and replaced with their likeness.
Two friends take jobs as truck drivers, unaware that the trucking company is being targeted by a gang of saboteurs who will stop at nothing, including murder, to stop them.
Topper is once again tormented by a fun-loving spirit. This time, it's Gail Richards, accidentally murdered while vacationing at the home of her wealthy friend, Ann Carrington, the intended victim. With Topper's help, Gail sets out to find her killer with the expected zany results.
Dr. Bernard Adrian is a kindly scientist who seeks to cure a young woman's polio. He needs human spinal fluid to complete the formula for his experimental serum. Meanwhile, a vicious circus ape has broken out of its cage, and is terrorizing the townspeople. Can there be a connection?
A none-too-popular (nor good) radio singer, Rita Wilson is murdered while singing on the air in a radio studio. Radio page boy, Frankie Ryan, and his janitor pal, Jeff, solve the mystery for the none-too-sharp police.
Twenty years removed from Alice Barlow's murder by a thief looking for her jewels, newlyweds Paul and Bella Mallen move into the very house where the crime was committed. Retired detective B.G. Rough, who worked on the Barlow case, is still in the area and grows suspicious of Paul, who he feels bears a striking resemblance to one of Barlow's relatives. Rough must find the truth before the killer can strike again and reclaim his bounty.
When the plane owned by the "Yukon and Columbia Mail Service" crashes, RCMP Sergeant Renfrew (James Newill) and Constable Kelly (Dave O'Brien) suspect murder. Their suspicions are confirmed when Renfrew finds the control stick has been jammed, forcing the plane to fly in one direction until the gas ran out. Mine owner Louise Howard (Louise Stanley) reports that her superintendent is missing. The Mounties find him murdered and that too has been made to look like an accident. A new mail service pilot, Bill Shipley (Warren Hull), arrives. He had gone to training school with Renfrew but had been cashiered for misconduct. The Mounties discover that Raymond (Karl Hackett), who had been working for Louise, really owns the flying line managed by Yuke Cardoe (William Pawley.) They find proof that all the gold from the mine isn't being turned over to Louise, and suspect that Raymond and Yuke are stealing the gold and shipping it to Seattle by plane.
While participating in a contest at a local newspaper in which school children are asked to submit a news story, local attorney Carson Drew's daughter Nancy intercepts a real story assignment. She "covers" the inquest of the death of a woman who was poisoned. Nancy doesn't think the young woman accused of the crime is guilty and corrals her neighbor Ted into searching for a vital piece of evidence and stumbles onto the identity of the real killer.
The second and final Grand National Pictures film to feature The Shadow, played again by Rod La Rocque. In this version, Lamont Cranston is an amateur detective and host of a radio show with his assistant Phoebe (not Margo) Lane. Cabbie Moe Shrevnitz and Commissioner Weston also appear.
Pepe Le Moko is a notorious thief, who escaped from France. Since his escape, Moko has become a resident and leader of the immense Casbah of Algiers. French officials arrive insisting on Pepe's capture are met with unfazed local detectives, led by Inspector Slimane, who are biding their time. Meanwhile, Pepe meets the beautiful Gaby, which arouses the jealousy of Ines.
Lamont Cranston assumes his secret identity as "The Shadow", to break up an attempted robbery at an attorney's office. When the police search the scene, Cranston must assume the identity of the attorney. Before he can leave, a phone call summons the attorney to the home of Delthern, a wealthy client, who wants a new will drawn up. As Cranston meets with him, Delthern is suddenly shot, and Cranston is quickly caught up in a new mystery.