Major Dennis, Danny, and Rex crack up their plane on the "Sitting Seagull", a floating laboratory working on inventions to prevent war. But a whale rams the ship, and Rex and Danny tumble aboard the whale. Swimming free, they reach a graveyard of wrecked ships - where Nazis hide out and plan to steal the "Seagull's" anti-war inventions! As Danny signals for help, ex-K-9 Rex knocks the Nazis flying just as help arrives.
A UFO buzzes town on the same day every month, and Bobo's latest craze is flying saucers. He even buys a spacesuit! Watching the skies, he finds crooks have rigged a saucer-rocket with jets. They capture Bobo and tie him atop, and he's launched! Bobo quote:" I thought spacemen travel inside a rocket - not on it!" High up, Bobo can see the crooks use the distraction to loot jewelry stores. He steers his UFO crack up their car. And with the reward money, buys weapons for his look-out station!
Rex rescues "Brownie", a lost pup, who trails him around. No one responds to newspaper ads, so Rex "adopts" Brownie and teaches him street smarts and crime prevention. Meanwhile an Egyptian exhibit is coming to town, and Danny takes Rex. Crooks pull guns to steal the gold artifacts, but Rex grabs the loot and alerts guards. Then he sniffs a familiar scent on the exhibitor's daughter. Clasping her hem, he tows her to - Prince, her lost puppy!