In an Author’s Note, an anonymous author figure explains that he traveled from his home in Canada to India because he was feeling restless. There, while sipping coffee in a café in the town of Pondicherry, he met an elderly man named Francis Adirubasamy who offered to tell him a story fantastic enough to give him faith in God. This story is that of Pi Patel. The author then shifts into the story itself, but not before telling his reader that the account will come across more naturally if he tells it in Pi’s own voice.

Part One is narrated in the first person by Pi. Pi from an advanced age, looking back at his earlier life as a high school and college student in Toronto, then even further back to his boyhood in Pondicherry. He that he has suffered intensely and found solace in religion and zoology. He how Francis Adirubasamy, a close business associate of his father’s and a competitive swimming champion, taught him to swim and bestowed upon him his unusual name. Pi is named after the Piscine Molitor, a Parisian swimming club with two pools that Adirubasamy used to frequent. We that Pi’s father once ran the Pondicherry Zoo, teaching Pi and his brother, Ravi, about the dangerous nature of animals by feeding a live goat to a tiger before their young eyes. Pi, brought up as a Hindu, Christianity, then Islam, choosing to practice all three religions simultaneously. Motivated by India’s political strife, Pi’s parents to move the family to Canada; on June 21, 1977, they set sail in a cargo ship, along with a crew and many cages full of zoo creatures.
At the beginning of Part Two, the ship . Pi clings to a lifeboat and encourages a tiger, Richard Parker, to join him. Then, realizing his mistake in bringing a wild animal aboard, Pi leaps into the ocean. The narrative jumps back in time as Pi describes the explosive noise and chaos of the sinking: crewmembers throw him into a lifeboat, where he soon himself alone with a zebra, an orangutan, and a hyena, all seemingly in shock. His family is gone. The storm dies down and Pi about his difficult situation. The hyena the zebra and the orangutan, and then—to Pi’s intense surprise—Richard Parker reveals himself: the tiger has been in the bottom of the lifeboat all along. Soon the tiger kills the hyena, and Pi and Richard Parker are alone together at sea. Pi on canned water and filtered seawater, emergency rations, and freshly caught sea life. He also for the tiger, whom he masters and trains.
The days slowly. During a temporary blindness brought on by dehydration, Pi has a run-in with another blind castaway. The two food and attach their boats to one another. When the blind man attacks Pi, intending to eat him, Richard Parker kills him. Not long after, the boat pulls up to a strange island of trees that grow directly out of vegetation, without any soil. Pi and Richard Parker here for a time, sleeping in their boat and exploring the island during the day. Pi discovers a huge colony of meerkats who in the trees and freshwater ponds. One day, Pi finds human teeth in a tree’s fruit and comes to the conclusion that the island people. He and Richard Parker head back out to sea, finally washing ashore on a Mexican beach. Richard Parker off, and villagers take Pi to a hospital.
In Part Three, two officials from the Japanese Ministry of Transport interview Pi about his time at sea, hoping to shed light on the fate of the doomed ship. Pi tells the story as above, but it does not fully satisfy the skeptical men. So he tells it again, this time replacing the animals with humans: a ravenous cook instead of a hyena, a sailor instead of a zebra, and his mother instead of the orangutan. The officials that the two stories match and that the second is far likelier. In their final report, they compliment Pi for living so long with an adult tiger.

Summary taken from sparknotes.com