The film features a psychosomatically mute English boy (Lester), who sights a wild, white pony on the Dartmoor moors and sets out to tame him.[3] He is supported by an old moorman (Mills) and a neighbouring farm girl, Fiona Fullerton. Much of the film is devoted to him searching for the pony and his family searching for him across the beautiful, foggy moors.[4][5]
A. H. Weiler of The New York Times wrote: "If it is not a milestone in its genre, its cloying quotient is decidedly low. As a dissection of the rapport between two youngsters and a couple of wild animals in a largely uncomprehending world, it has enough honesty and genuine sentimentality to move mere grown-ups too."[6]Roger Ebert of the Chicago Sun-Times gave the film three stars out of four and called it "a sensitive and beautiful film, and probably ideal for kids from about the fourth grade up."[4]Gene Siskel of the Chicago Tribune also gave the film three stars out of four and wrote, "On the face of it, the film seems pat ... But the well-written script departs from tradition and gives us a story full of unpredictability and insight."[7]Kevin Thomas of the Los Angeles Times wrote: "Quite unabashedly, Run Wild, Run Free celebrates the power of love, yet it happily avoids the treacle – except for an overripe score – that characterizes most pictures about children and animals. It pulls out all stops emotionally but gets away with it because it has simplicity and intelligence."[8]The Monthly Film Bulletin wrote that "Richard Sarafian's combination of generally pedestrian images with a quivery, quavery wild-heart-of-Dartmoor sensitivity suggests some uncertainty as to whether the picture is aimed at the pony club set, or their more susceptible mothers and grandmothers."[9]