A young couple are killed in a plane crash in the jungle. A monkey brings the infant survivor of the crash to Tarzan (Johnny Weissmuller) and Jane (Maureen O'Sullivan) who name the child, Boy. Five years later, a search party (Ian Hunter, Henry Wilcoxen, Frieda Inescort and Henry Stephenson) come looking for the child who is heir to a fortune. They wound an elephant after which they get into a scrape with the Gaboni tribe but Tarzan arrives to call off the natives. Jane cooks them a meal of ostrich egg and tells them that they buried that there were no survivors of the plane crash. Boy appears in many of the scenes: swimming, playing with the animals, impressing the visitors and being rescued from a spider web, a waterfall and a rhino by Tarzan. The party learn that Boy is their relative and insist on taking him back with them. Tarzan steals their guns at night and tosses them into a pool while Cheetah awakens the party by taking their photo with a camera he has found. They refuse to leave without their guns so Tarzan dives for the guns but he is left stranded.. Against Tarzan's advice Jane is persuaded to help lead them out of the jungle so that they can return Boy to civilization.  Sir Thomas, the only good guy  in the party, is killed by his nephew while trying to warn Jane that she has been duped. Refusing to follow the route chosen by Jane the party is then captured by the savage Zambele tribe. Jane helps Boy escape and he runs through many jungle obstacles to get back to Tarzan. He is unsuccessful in getting a rope to Tarzan in the pool so he gets elephants to push a dead tree down to the stranded apeman. Tarzan and Boy, the great apes and an elephant herd.all race to the village to rescue the surviving members of the party.  Jane has been seriously wounded by a native spear. In the original script she dies from the wound but following a barrage of protests from fans... and ERB... the studio resurrected her and had her recover in Tarzan's arms. The Tarzan family return to their idyllic life in the jungle.

CAST
Johnny Weissmuller: Tarzan
Maureen O'Sullivan: Jane
Johnny Sheffield: Boy (as John Sheffield)
Ian Hunter: Mr. Austin Lansing
Henry Stephenson: Sir Thomas Lancing
Frieda Inescort: Mrs. Lancing
Henry Wilcoxon: Mr. 'Sandee' Sande
Laraine Day: Mrs. Richard Lancing
Morton Lowry: Mr. Richard Lansing
Gavin Muir: Pilot (uncredited)
Baby X: Boy as a younger child. (uncredited)
 

82 min ~ B&W (Sepiatone) ~ Mono (Western Electric Sound System)
Technical Specs: (8 reels) 35mm negative & print ~  Spherical ~ Aspect ratio 1.37 : 1
Production Companies: Loew's Inc.~ Metro-Goldwyn-Mayer Pictures
Distributors: Loew's Inc. ~ Metro-Goldwyn-Mayer Corporation
Production Date: January 9, 1939
Copyright Holder: Loew's, Inc.; 8 June 1939; LP8906
Other Companies: The Hagenbeck-Wallace Circus provided elephants for stampede
Release Dates: USA June 16, 1939 ~ Canada July 12, 1939 (Toronto)

• The working title of the film was Tarzan in Exile -- referring to Tarzan's self-imposed exile following the death of Jane.
• In the original script Jane was to have died (Maureen O'Sullivan wanted out of the Tarzan series). Fan protest forced a last-minute rewrite in which Jane recovers from her near-fatal wound, admitting she had been wrong to disobey Tarzan. She was offered raise and stayed on for one more film in the series. 
• Most of the film was filmed on studio sets with almost all the location footage taken from other films including Baboona (1935), Trader Horn (1931), Tarzan the Ape Man (1932), and Tarzan and His Mate (1934).
• For the many swimming and underwater sequences, Weissmuller and Sheffield were sent with Baby Bea the elephant and a large sea turtle to Crystal Springs, Silver Springs, and Wakulla Springs, Florida, USA.
• Pregnant Maureen O'Sullivan stayed in Hollywood and a double was hired to do her Florida swimming scenes.
• At the conclusion of the Florida shoot, Johnny Weissmuller presented his loin cloth, signed by cast and crew, to Wakulla Springs co-owner "Shorty" Davidson.
• In response to Maureen O' Sullivan's refusal to do more Tarzan films screenwriter Cyril Hume was directed to write Jane out of the film series.  Hume suggested that they add a son so as to retain the family audience after Jane's death. Fearing that the Legion of Decency would object to a child out of wedlock he had them find a child survivor of a plane crash.
• Weissmuller's personal choice for the role of Tarzan's adopted son, Boy, was five-year-old Johnny Sheffield, son of British actor Reginald Sheffield.
• When Burroughs learned of the planned death of Jane he wired MGM from Hawaii, threatening to sue. There was nothing in Burroughs' contract with the studio to prevent this script decision but the backlash from fans was so overwhelming that they changed the script.
• August 29, 1939: ERB, who was highly critical of the plans to eliminate Jane in Tarzan Finds a Son, wrote producer Zimbalist voicing approval for the job he had  done.

The New York Times
In the escapist heaven of the cinema, there is only one Tarzan, and Metro-Goldwyn-Mayer's is the profit. For this Tarzan, time does not exist: Johnny Weissmuller is merely his current incarnation. But the question of issue was bound to arise sooner or later, and Metro seems to have answered it in the handsomest and most hygienic fashion with the chapter self-explanatorily entitled "Tarzan Finds a Son," at the Capitol. The child, and a darned convenient
brat he is for plot purposes, is dropped from the African skies not by the stork, but buy an Imperial Airways liner which crashes in the jungle not far from the arboreal penthouse of the Tarzans, with its elephant-operated lift, its chimpanzee house maid, its one ape-power revolving fan, its couches upholstered in Zebra-hide, like El Morocco.

To get milk for that first bottle, Tarzan, the fleet-footed, runs down and catches a she-antelope; the poor thing, not unnaturally amazed by such phenomenal track prowess, finally just gives in quietly. In no time at all, a cunning rattle and a swinging cradle have been devised by the doting foster-parent, and before you can say "Boy" (which is the name Tarzan paternally bestows upon him) the lad is swinging expertly about on the jungle creepers, like a chimp off the old block. And that's when the safari five years later, that is with Ian Hunter and all those people with Mayfair accents, shows up looking for news of the passengers on that ill-fated plane. Need we add that "Boy" is the heir to a title and vast estates back home? Of course we needn't.

Nor need we bore you with our feeble efforts to depict how complete a cad Ian Hunter turns out to be; you know how disagreeable people can become when they see any prospect of losing an inheritance. Enough to report that the rest of the picture is a circus, a water (and an underwater) carnival, a rodeo, with Tarzan in a big rhino bustin' scene, a teeming jungle film, perfectly silly, of course, but for the purposes of the young and of the obstinately unadult, as much fun as a barrel of monkeys.

It seems almost priggish to breathe a word of criticism against so disarming a production, yet Metro might be gently chided for such monstrosities as a lion in a tree, apes riding elephants to the rescue. Also, you would think Tarzan's language might have improved a bit after all these years of exposure to Maureen O'Sullivan's impeccable diction, but it hasn't. He still grunts like a Creek Indian, and articulates in a minimum of words, without conjunctions.
 
 
 

Variety
"Tarzan Finds a Son" carries more credulity and believable jungle adventure than the long list of preceding Tarzan features unwound at intervals during the past 20 years. Ape-man's chummy attitude with the wild beasts of the jungle, and his tree-swinging acrobatics elaborated on previously, have been minimized here.

Picture is a cinch setup for the kids and may catch on for nominal bids in the action houses. It's under a handicap due to absurdities and wildly impossible situations identified with Tarzan and spread pretty thick in the several preceding Tarzan features and serials turned out in sound film.

Tarzan and the missus save a baby in a wrecked plane that crashes in the jungle. At age of five, Tarzan is proudly teaching his accepted son the jungle lore, when a searching party arrives to establish death of the baby, who has come into heavy inheritance in England. Ian Hunter and Frieda Inescort are out to grab the inheritance for themselves, and start plotting death of Tarzan and snatch of the youngster. But while they are at cross-purposes with
Tarzan, the Missus consents to trip of the kid to the outside and accompanies the party through a savage tribe domain. Natives capture the safari and start a wild celebration of death in their village. Boy escapes through stockade to bring Tarzan and herd of elephants to completely wreck the village in a wild stampede that routs the savages.

There are animal thrills and stunts aplenty throughout the picture. Stock shots of wild life have been neatly intercut; while a fight between hyenas and leopards in the jungle is a thriller. Naturally youngster's wanderings from the jungle home provide opportunity for the kid to be chased and he is on several occasions by rhinos, alligators, lions and hyenas. Youngster also goes perilously near the falls for a rescue by Tarzan; and at another point is saved in the
nick of time from the web of a tarantula tribe.

Underwater episodes in which Tarzan and Boy play for long periods is exceptional and highly interesting. For added interest, baby elephant pal of the boy is along for some splashing, and this episode is a top spot in the picture.

Johnny Weissmuller has made three previous Tarzan features, and athletically runs and swims through as the ape-man in okay fashion. Miss O'Sullivan is the jungle wife, and gets in some good dramatic work in battling against herself to give up the youngster to the outsiders. Tarzan's boy, little John Sheffield, does nicely and performs his chores athletically. Kid takes direction easily, and might get over in other pictures aside from the Tarzan group.
Balance of cast is nicely set up for what they have to do.

Productionally, picture is top grade in all technical departments. African jungle locale is one of the best jobs of its kind turned out in Hollywood for some time. Camera work throughout is excellent same goes for the sound department, which blended the jungle sounds for background effects on the sound track. The underwater shots, taken in Florida, will merit attention from technical standpoint.

With a minimum of dialog, and script concentrating on action and animal antics, picture is a likely setup for good biz in the foreign field; requiring minimum of voice dubbing..

Richard Thorpe's direction moves along at a speedy pace, and he takes fullest advantage of cute antics of the ape Cheta, and the baby elephant for some elemental comedy.

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From "Argonotes, The Readers' Viewpoint" in the September 9, 1939 issue of Argosy

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An open letter to Hollywood from a confused but eager-to-be-enlightened Tarzan-devotee: 

The Hon. Mr. Metro-Goldwyn-Mayer 

Dear Leo: 
   In a restless moment the other sultry night, we went to see your film, Tarzan Finds a Son. That was the one, in case you don't remember, in which the Lord of the Jungle had a baby laid on his doorstep by a careless aeroplane. 
   When some English rascals came along to take him back to London, Tarzan -- for some reason which was never entirely clear -- refused to give him up. (The English rascals only wanted him for his money; otherwise they wouldn't have been caught dead with him around the house, and I don't blame them.) 
   The picture ends on a distinctly somber note: Tarzan gets to keep the boy -- and I'll bet he regrets that by now; and Ian Hunter, who has hitherto escaped the bitter fate of cinematic marriage to people like Kay Francis and Jeannette MacDonald, is more or less dismantled by bloodthirsty savages. 
   All this merely to refresh your memory. What we're really trying to get straightened out are the baffling blood-ties of the Greystoke clan. We distinctly remember, when Mr. Burroughs first started to write about Tarzan in this magazine, that Tarzan was the missing Earl of Greystoke, sole male survivor of that distinguished and fantastically wealthy family. 
   But in Tarzan Finds a Son, the other characters keep murmuring that Boy (Tarzan called him that -- I should have preferred Little Scorpion) is the nephew of Lord Greystoke. Tarzan's nephew, do you mean? But in that case Tarzan would have had just as much right to be his guardian as Ian Hunter and Frieda Inescourt, who played lesser Greystokes. 
   Or is this entirely some other branch of the family? Do all Greystokes become Missing Heirs the moment they get near the Africa jungles? Can't any of those people ever get where they're going without being abducted by gorillas or wrecked in a plane? The Dithering Greystokes, that's the way we'll have to think of them. Why, they can't even cross Picadilly Circus without becoming hopelessly lost. So whatever makes them think they could cope with the Dark Continent? 
   At this rate, the Greystokes are going to be in a dandy spot to hold a Big Family Get-Together just west of Mombesi. We'll try to make it if we can possibly get there. Meanwhile, could you straighten the Greystoke genealogy out for us a little? 
   Your admirer, 
   Hamilcar Ishwerwood (né Greystoke) 

Contributed by Steven Utley