Peru, 1927. Captain Walter Snetterton sets out on a pioneering expedition to observe the adaptability of frogs to hostile environments, by exposing them to one of the most inhospitable mountain ranges on earth.
Arriving in the village of Quequeña, his men laden with boxes of frogs, he discovers the locals listening to football on BBC radio, something that continually distracts them from attempts by Snetterton and his faithful RSM, to introduce themselves. Finally, they meet Gregory, the local Vice-Consul, who is more interested in drinking and womanising than in helping the expedition, and who points out that guides are hard to come by at this time of year, as the Cup Final is swiftly followed by Wimbledon.
Finally, Gregory comes up with a guide, a tiny old lady who turns out to have the sure-footedness of a mountain goat. Indeed, so fast is she that Snetterton and the RSM are compelled to shout after her, but linguistic difficulties cause a misunderstanding that leads her to procure two schoolgirls for the men instead.
A thunderstorm that night causes the frogs to become restless. While Snetterton explains their communication methods to the RSM, they are interrupted by Corporal Johnson, who informs them that the natives have captured one of the frog boxes. The box is retrieved, but Gregory explains that the natives believe that the frogs brought on the thunder - which isn't actually thunder, but the volcano El Misti about to erupt, which affects the radio reception. Snetterton puts the RSM in charge of guarding the boxes full time.
The following night, the RSM disappears. Snetterton and Johnson look anxiously for him, and only find him the next morning - he's spent the night with one of the village girls. Declaring that he has fallen in love, he resigns his commission. Snetterton goes in search of Corporal Miller, who is supposed to be guarding the frogs, but who is also consorting with the natives - as is Corporal Johnson. Meanwhile, the frogs have escaped, with the understandable exception of the Himalayan Sleeping Frog.
Gregory commiserates with Snetterton, who angrily claims that he's still going ahead with the expedition. One of the natives turns the radio on and listens to the Wimbledon commentary. In a rage, Snetterton shoots the radio. The natives' mood switches instantly from apathy to anger, and he is forced to flee.
Nothing more is ever seen of Snetterton, but the frogs that escaped hop six thousand three hundred miles north to Mexico City, in the process demonstrating all of Snetterton's theories about amphibian high-altitude survival to perfection.
