The story is set after the Second Afghan War (which ended in 1881), but before the Third (fought in 1919), probably in the period of 1893 to 1898.[3]
Kim (Kimball O'Hara) is the orphaned son of an Irish soldier (Kimball O'Hara Sr., a former colour sergeant) and a poor Irish mother (a former nanny in a colonel's household) who have both died in poverty. Living a vagabond existence in India under British rule in the late 19th century, Kim lives by begging and running small errands on the streets of Lahore. He occasionally works for Mahbub Ali, a Pashtun horse trader who is one of the native operatives of the British secret service. Kim is so tanned and immersed in the local culture that few realise he is white.
Kim befriends an aged Tibetan lama on a quest to free himself from the Wheel of Things by finding the legendary "River of the Arrow". Kim becomes his chela (disciple) and accompanies him on his journey, initially walking along the Grand Trunk Road. On the way, Kim learns about the Great Game and is recruited by Mahbub Ali to carry a message to the head of the British Secret Service in Umballa.
Kim encounters and recognises his father's regiment on the march. Curious, he sneaks in when the soldiers camp for the night. He is caught and mistaken for a thief, but the regimental chaplain identifies Kim by his Masonic certificate, which he wears around his neck. Upon learning of Kim's connection to the regiment, the lama insists that the boy comply with the chaplain's plan to send him to an English school in Lucknow. The lama, a former abbot, pays for Kim's education.
Throughout his years at school, Kim remains in contact with the holy man he has come to love. He is also trained in espionage (to be a surveyor) while on vacation from school by Lurgan Sahib, a sort of benevolent Fagin,[4] at his jewellery shop in Simla. As part of his training, Kim is given brief looks at a tray full of mixed objects and notes which have been added or taken away, a pastime still called Kim's Game, also called the Jewel Game. Other parts of this training are disguise and the careful study of the Indian population, and the characteristic dress, behaviour and "even how they spit" in order to go undercover or to uncover those in disguise. He also accompanies Mahbub Ali on one school break; when he proves apt at spying on and evaluating how to capture the city of Bikanir, Mahbub Ali persuades his superior, a skeptical Colonel Creighton, that the boy is ready.
After three years of schooling, Kim begins to take part in the Great Game, joining the Secret Service at 20 rupees a month. Kim rejoins the lama and at the behest of Kim's superior, Hurree Chunder Mookherjee, they make a trip to the Himalayas so they can try to find out what a couple of Russian intelligence agents, one Russian and one Frenchman, are doing there. Kim obtains maps, papers and other important items from the Russians, who are working to undermine British control of the region. Mookherjee persuades the Russians to hire him as a guide. When the Russian strikes the lama in the face, Kim attacks the man, then flees when shot at, while the outraged porters abandon the party and take the lama away to safety.
The lama realises that he has gone astray. His search for the River of the Arrow should be taking place in the plains, not in the mountains, and he orders the porters to take them back. Here Kim and the lama are nursed back to health after their arduous journey. Kim delivers the Russian documents to Hurree, and a concerned Mahbub Ali comes to check on Kim.
The lama finds his river and is convinced he has achieved Enlightenment, and wants to share it with Kim.
