It's not really a spoiler to say that George unintentionally orphans three lion cubs when he kills a lioness in self-defense, leading him and his wife to decide to hand-raise the trio. Joy Adamson becomes particularly attached to the runt of the litter, whom she names Elsa after a school acquaintance, but finds it increasingly difficult to accept that she will have to part with the growing cub as she reaches maturity. And, as the saying goes, thereby hangs the rest of our tale.
Contemporary viewers, especially adults, are likely to be somewhat jarred by some aspects of the film that seem quite dated today. With one exception, the Adamsons' native staff are interchangeable figures with no role except to provide -- well, one is almost tempted to say "local color." At one point George is even referred to as "bwana," which sounds like a term one would associate with a movie of the 1930s, not the 1960s. One also wonders why the lion that attacked a woman at the beginning of the film wasn't darted and relocated to a more remote area instead of being hunted down and killed, which (one would hope) would be done today. It's important to remember, however, that although this was filmed in 1966, it's based on Joy's 1960 memoir about raising and then trying to return Elsa to the wild; that publication date confirms that these events occurred even earlier, in the mid-1950s.
Still, the most enjoyable part of the film is undoubtedly the animal antics involving the three cubs, especially when they are young and still manageable. Disney, in particular, used to spool out films reminiscent of this part of "Born Free" almost effortlessly during this same time period -- think of "Charlie, the Lonesome Cougar," "Joker, the Amiable Ocelot," or "An Otter in the Family." But any notion that this might have been a Disney film is soon dispelled -- how many Disney films, after all, depict a human killed by a lion, and two great wild animals shot to death, all in the first 10 minutes?
The two main actors nevertheless do a fine job, abetted no doubt because Bill Travers and Virginia McKenna were a real-life married couple when this was filmed. They have great chemistry together, and their relationship seems almost too good to be true; indeed, when George turns on Joy angrily at one point, it's a jarring moment because it's unlike anything that's come before.
Things were not quite so idealized between the actual couple -- although they never divorced, the real-life Adamsons drifted apart toward the last decade of their lives. And Joy (which was a nickname) was actually Austrian, not British, and one suspects that she might not have spoken with Virginia McKenna's clipped British accent. Indeed, according to this very website, the real Joy Adamson did not live up to her nickname, becoming such a problem during filming that she was banned from the film set.
The movie has an interesting legacy. During the 1970s, it became an annual "television event," almost like "The Wizard of Oz." There were several follow-up films -- some documentaries, some scripted -- based in part on later memoirs by Joy Adamson. The real Ms. Adamson, sadly, came to a bad end, as she was murdered in 1980 by a disgruntled former employee. George, too, met a violent death, killed by a poacher (although he saved a woman's life in the process). The happiest consequence were the remaining lives of Virginia McKenna and Bill Travers, who became animal activists, making other animal-related films, and trying among other things to save animals kept in appalling conditions in cheaply-run zoos. They established a foundation, named after the film, that continues their work under the direction of one of their children.