Small World is a tale about the comings and goings of a group of English language and literature scholars. It begins with Persse McGarrigle, from a small Irish college, attending his first conference at a small English college that has never before hosted a conference. Persse, along with the readers, learns the role conferences play in academia: a little work teamed with as much fun as possible. Along with several more experienced colleagues, Persse pursues a beautiful participant whose name badge reads A L Pabst. Persse falls in love with her and arranges (he thinks) a tryst, but she tricks him and departs, leaving no way to contact her. In Rummidge, Persse also learns that his cousin Bernadette has dishonored herself and been cast out by the family.

Hunting for Bernadette, whose stage name is Marlene, Persse finds indications that Angelica (A L Pabst) also leads a second life in the sexual underground as a pornographic performer, Lily. Persse can find neither woman's elusive trail and returns to teaching. Fate intervenes, however, and Persse wins a ?1,000 prize for his poetry, which will make searching for the fallen women possible. He first tries Amsterdam, where Angelica has told him her father was an executive for KLM at the time of her adoption. There he learns only Hermann Pabst has relocated to Los Angeles. He sees another disgusting poster of Lily but has no way of reaching her.

Thwarted again, Persse helps direct a literary retreat and happens to run into his cousin's rapist under conditions that allow him to obtain a support agreement. This in hand, Persse sets off on the cold trail, which passes through Switzerland, to Los Angeles (where he meets Hermann Pabst and obtains the full story about the identical twins), Honolulu, Tokyo and Seoul. By Hong Kong, Persse is broke. We meet him again in Jerusalem, which he reaches on foot over the desert from Aden.

Meanwhile, other characters are leading interlacing lives. Philip Swallow and his wife Hilary in Rummidge are drifting apart but remain married. Philip travels to conferences as often as possible. Years ago he and Morris Zapp exchanged faculty positions - and wives. Dysirye Zapp divorces Morris and bases a novel on him, which makes her rich. She is frustrated by writer's block on a new project. Before flying on to additional conferences, Zapp hears Swallow's story about his affair in Italy with Joy Simpson, who subsequently dies. When Swallow flies off to Turkey to deliver a series of lectures, he discovers that Joy is very much alive and their union has produced a three-year-old daughter. They plan to marry as soon as Hilary agrees to a divorce, but Swallow is loath to ask for one until she gets established in her new profession, marriage counseling.

Zapp, meanwhile, after an uncomfortable liaison with Fulvia and Eduardo Morgana, is kidnapped in Italy by their leftist friends who believe rich Dysirye will ransom him. Dysirye negotiates the kidnappers down, and she is ready to hand over the sum when Fulvia warns the kidnappers to release him for free. Feeling he has received a new lease on life, Zapp flies to Jerusalem and runs a laid-back conference. Rodney Wainwright, an unprepared lecturer from Australia, receives a miracle when Swallow appears to have come down with Legionnaire's Disease. Everyone scatters. Zapp and Thelma Ringbaum become involved, while Swallow and Joy go their separate ways.

In December, the whole world of English scholarship gathers in New York for the MLA convention. There Persse finds and makes passionate love with Angelica, before discovering it is her prostitute twin, sent to break the news to him that Angelica is engaged to someone else. Venerable Arthur Kingfisher, who has been evaluating contenders for a UNESCO chair, surprises everyone by emerging from retirement to accept the post himself. He announces he will marry his beautiful young Korean assistant and is then confronted by the fact that he is the Pabst twins' biological father by a retired spinster teacher who has been appearing throughout the novel. Persse flies back to Heathrow on New Years Eve to find the British Airways employee who has several times been a nexus of the novel's action and whom he last time saw weeping over his devotion to Angelica. Cheryl has been fired and disappeared somewhere in the small, narrow world, and Persse is determined to find her.