Diet Smith calls Dick Tracy, excited beyond all belief. He’s just gotten back from his third expedition to the Moon and after returning home he founds he has brought home a stowaway Maid from the Moon! This Moon Maid astounds everyone, show cases her strange temperature and electrical powers by turning ice to water and disabling T.V. cameras while dancing in the snow. Junior and an ape named Droopy are nearly hypnotized by her and the learn from her strong reactions to Moon photos that she doesn’t want to return to her home.
Finally Junior is able to settle her down by drawing sketches and soon he has tought her to paint, which she does amazingly well. Federal men arrive to take Moon Maid away but she easily knocks them out cold and goes running off into the mountains where she saves a freezing woman and a newborn baby with her warmth. Moon Maid is herself nearly killed during the rescue as she dangerous depletes her power but she recovers quickly.
Lizz opens up her home to Moon Maid for a party and asks Junior to invite some friends to get her to socialize with others her age. This goes awful after she burns a dress she is given by the other kids and Moon Maid breaks into tears because she is not human and Lizz consoles the young woman from the Moon. After the incident Tracy thinks Moon Maid should be sent back home. Junior disagrees strongly, but Dick and Diet Smith decide it would be for the best and ready a Space Coupe. Junior has fallen in love with Moon Maid and wants to get married, he and his love slip out at night and take off with the Space Coupe. Joy riding for a while, the love birds set course for the Moon and Tracy is very upset with himself for driving Junior away. Nothing will console him and Dick quits the police force to find his son.
Moon Maid and Junior land in Moon Valley, the only place on the Moon with vegetation, atmosphere and livable temperatures thanks to some hot springs. There he meets Moon Maid’s family, including her father the Governor of the Moon. Dick Tracy and Diet Smith take a second Space Coupe and head off to the Moon on their own. They are first pinched by the local guardians flying thimble like air cars and are then held prisoner in a force field prison.
Diet and Tracy are eventually released from prison and reunited with Junior and Moon Maid but the Earthlings (including Junior) are quickly put back in prison. Shortly, Moon Maid brings the prison guards some drugged Escargot (the Moon people’s favorite delicacy) and as the guards nod off she turns off the force field. The four escape back to Earth in one of the Space Coupes.
Meanwhile in a sub-plot, a skeleton is found in the core of a tree and forensics show the body has been there since 1918 along with a whisky bottle with a good set of fingerprints. The mystery puzzles Sam and the remainder of the police force and they make no progress on the case.
On her return, Moon Maid is flooded with requests from colleges across the country to come lecture them about the Moon. She wants to learn more about the Earth before she and Junior get married and off she goes. Junior arranges a $1000 speaking fee so they will make some money during the trip. Moon Maid’s “lectures” are more like carnivals to showcase her powers to students and faculty at these colleges (Harvard, Yale and Michigan and Knox College are shown).
Meanwhile, Tracy can’t resist the call of the detective department and rejoins the force (Sam and Patton dance a jig). Investigating the case of the skeleton found in the core of a tree, he learns from Sam that the property was once owned by two men, Mr. Jade and Mr. Smitz back in 1910. Both men are dead, with Jade having been lost at sea in 1918, but his son Chet Jade is a cartoonist with a team of four artists who help him draw a comic strip called “Sawdust”. Sawdust is a very simple strip in which little dots of sawdust talk and make jokes.
Tracy has determined that the tree was split and repaired so that the body could be hidden and Tracy spends a great deal of time with the cartoonists, suspicious of Chet Jade’s father or his partner. He first finds a surprising amount of empty baby food containers in the trash and later When he discovers that the attic doorway has been boarded up he and Sam decide to check the attic. They first attempt to scale the house, but an unseen bony arm reaches out an knocks away Tracy’s grapple and Sam and Dick leave when they hear some disturbing Moon news.
Earth detects a Space Coupe flying quickly towards them from the Moon. Moon Maid’s father and his wife found the Space Coupe Junior and Moon Maid left behind and after a few tense moments they broadcast that they come in peace. After landing, the Governor apologizes to Diet Smith and Tracy for the way they were treating in Moon Valley and he presents them with gifts including crystalized carbon, a massive haul of precious gems and four flying air cars. (The thimble shaped cars). Moon Maid’s parents reconcile with her and bless her coming marriage and Sam and Dick spend some time learning to fly the air cars.
Tracy has an idea and he and Sam take the air cars to the Jade home and fly up to the attic window where an emancipated old man attempts to fire a shotgun at them. The shotgun, with ammunition many decades old will not fire. The man then attempts to kill himself, but the ammunition in his handgun also refuses to fire and Tracy climbs in the window and kindly disarms him. This man is Chet Jade’s father and with his son present he tells the story of how his partner Smitz and he disagreed on the sale of the old Nursery and how Smitz had attacked him with a knife. Drunk at the time, old Father Jade shot his partner dead and then enlists his small son to help him hide the body. After the fact, Father Jade suffered terrible guilt and gave up alcohol and hid himself in his attic, eating only baby food because of his ulcers. Chet Jade admitted to caring for his father and keeping him hidden. After the tale, Father Jade dies naturally and Tracy considers the case closed.
Finally, a grand banquet and reception is held with consumption of Giant Escargot and much dancing by Moon Maid and presumably others. Moon Maid and Junior are married while Diet Smith and the Governor of the Moon engage in a technological contract with each other, giving Diet technology he so wants and the Governor the titanium he would need to create Earth objects (like the Space Coupe). Diet Smith also give a presentation to the Government on how the Space Coupe was constructed.
Dick Tracy’s department receives a teletype from the FBI asking them to guard a secret shipment coming in from Kuykol off the North coast of Alaska. Sam is the first to arrive and is astounded to see the shipment is a thick chunk of ice with a woman wearing aviatrix clothing inside. While Sam and Tracy wait for a scientist named Doctor Ludwick Frost to arrive, they look closely at the ice and deduce that the woman is probably Lita Flite, an aviator who was lost at sea after her plane ran out of fuel crossing the Pacific in 1937. The fact the body was found way off course in Alaska is confusing.
Dr. Frost arrives and does studies on the ice (without breaking it) and Tracy watches for a while, convinced something is not quite right. Up in the Artic, government employees find a crashed plane and Tracy is ordered north to lend his expertise. No body is found in the wreckage, but the plane is not the one flown by Lita Flite. This plane was equipped for combat. While Tracy is away, Lizz helps Ludwick Frost with his studies of the Aviatrix and becomes uneasy by his obsession with the woman.
Tracy returns to the states just as the Aviatrix’s body is taken and Dr. Ludwick Frost goes missing. A container truck is found by police along the side of the road and Tracy suspects it was used to transport the ice coffin. As Tracy takes a sample of the water from inside the truck (hoping to match it to shavings of the ice block) Dr. Frost appears with two men in a fuel truck. They lock the trailer with Tracy inside and douse it with gasoline, lighting it afire. Tracy frantically calls Sam with his wrist radio and police race to put out the fire before Tracy is incinerated. Tracy would survive, exhausted by unharmed.
During Dr. Frost’s speeding getaway from the blazing truck, his vehicle goes out of control on the ice and the body of the Aviatrix flies out the back at high-speed, getting lost in a gulch. Dr. Frost has even more bad luck as his vehicle ends up in a tree and he is killed in spectacular fashion. Police are again called to this crime scene, and Tracy determines the ice coffin must be lost somewhere in the snow nearby.
A search is mounted while at the same time, another Doctor Ludwick Frost shows up at the station. There is some confusion, but this Dr. Frost is able to prove he is the real deal and the FBI learns the other Dr. Frost was in fact Eric Von Rhino, of an enemy’s secret police and former head of their aerial spy ring. Von Rhino once worked with a woman known as Trinka, and they put the evidence together that Trinka shot down Lita Flite over the Pacific, took top-secret information she was carrying but Trinka herself crashed in the Arctic in 1937. When her body turned up, Von Rhino sought to dispose of the evidence.
Tracy spends time alone in the snow and finally tracks down the ice coffin but two men in ski masks have beaten him to the find and chopped the body out of the ice. The men fire on Tracy and he returns fire, shooting one in the head and wounding the other, taking possession of Trinka’s body.
Nearing Christmas, Junior and Moon Maid return home after their wonderful honeymoon on the Moon. And Tracy family with their new member celebrate a happy Christmas.