Two aliens, Nukie and Miko, crash on Earth and are separated, with Nukie ending up in the African savanna while Miko falls into the hands of the Space Foundation in the United States. Miko reaches out telepathically to Nukie to explain that she is being held captive, setting a quiet, hopeful tone that threads through the story. The head of the Space Foundation operation, Dr. Norman Glynn, sends Dr. Eric Harvey to Nairobi to investigate the other crash site, and their experiments reveal a remarkable truth: Miko is a being made of pure energy.
Nukie begins to explore his surroundings and encounters two children, Tiko and Toki, who can understand him. They pledge not to reveal Nukie’s presence, creating a fragile bond built on curiosity and trust. The head of a Catholic mission, Sister Anne, is alerted by radio that Dr. Harvey is on his way, adding a human frame to the alien encounter. Nukie also meets Charlie, a talking chimpanzee, who speaks with him but claims ignorance about America. The The Corporal arrives and shoots at Nukie, yet the alien teleports to safety and, in the process, saves Tiko and Toki from a dangerous mountain lion. Inspired by the encounter, the boys agree to help Nukie find America, and Nukie even tries to commandeer Dr. Harvey’s helicopter—though the attempt ends in a crash.
Back at the Space Foundation, Miko has befriended the supercomputer known as E.D.D.I and persuades it to scan for Nukie. Dr. Harvey repairs the helicopter and departs to track the signal, while Tiko and Toki are brought before the tribal chief, Sangoma, and banished for bringing Nukie into their world. The two boys later reunite with Nukie, who expresses disappointment over their banishment but remains determined to help his companion. Tragedy strikes when Tiko is bitten by a cobra and taken back to camp by Dr. Harvey, just as the Corporal arrives to tranquilize Nukie. The tribe carries Nukie back to the village, and Tiko shares news of Nukie’s capture with Dr. Harvey and Sister Anne.
E.D.D.I continues to hunt for Nukie and ultimately locks onto Toki. Meanwhile, Toki discovers that Nukie is imprisoned in a cage and slips into the Corporal’s truck as he transports Nukie, freeing him at a trading post with Charlie. The Corporal finds Toki and holds him at gunpoint as Nukie and Charlie escape; Sister Anne distracts the corporal long enough to allow their flight. Nukie then finds Tiko in the infirmary and heals him as Toki and Charlie arrive. The trio decides to leave Tiko to recover and press on toward America.
Sister Anne makes another attempt to reach Dr. Harvey, but learns he has already left for America, while the Corporal continues plotting to sell Nukie. E.D.D.I manages to free Miko but cannot bypass the base’s security; Miko ultimately escapes with help from Pamela Carter. Nukie and Toki run from the Corporal, who drives off a cliff into a river and tumbles over a waterfall, injuring Nukie in the chaos. With communication momentarily broken, Nukie suggests they attempt flight, and they manage a partial ascent before Nukie collapses from exhaustion.
Toki wishes for his family, along with Miko and Nukie, to be with him, and soon Tiko, his mother, and Sister Anne arrive to confirm that Nukie is not a bad omen but a friend in need. Nukie appears in his light form as Dr. Harvey lands the helicopter, bringing Miko with him. The two aliens greet each other and inform the humans that they must leave. The adventure closes on a hopeful note as Charlie asks to join them, and the three dissolve into balls of light to fly away, signaling a quiet, transcendent ending to their Earthly visitation.
