Homer's original epic poem The Odyssey plays with different timelines, with some of the 10-year narrative occurring via flashbacks or recounting of past events. In that way, it's the ideal story for Christopher Nolan to tackle, as he often plays with time like putty, reshaping each of his narratives through different timelines or perspectives. As a result, his adaptation of The Odyssey unfolds with two main storylines, one of which occurs over a span of days, while the other occurs over a ten-year period.
The narrative surrounding Odysseus' son Telemachus, along with his mother's final challenge to the many suitors gathered in their home, technically takes place at the very end of Odysseus' journey, despite it being presented almost concurrently. Most of the major events themselves occur in long flashbacks, as Odysseus' "present" takes place at the end of his seven-year stay with the mystical nymph Calypso, as he describes his journey to her as she releases her hold over his mind. To fully grasp how the entire narrative plays out, it can be helpful to look at Nolan's record-breaking The Odyssey through a chronological lens.
The Trojan War
Odysseus actually spends 20 years away from his wife, son, and home of Ithaca, as the Trojan War itself lasted for ten years, most of it with the Greeks camped on the beaches outside the walls of Troy. Odysseus' plot with the Trojan horse final breaks the siege, and the Greeks overrun and destroy the city in a single night. After celebrating the victory, the three Greek kings (Odysseus, Menelaus, and the commander-in-chief Agamemnon go their separate ways to return home, with each journey meeting disaster at some point.
Agamemnon's Return Home
While Menelaus was blown off course and stranded at various points of the Mediterranean region for seven years, Agamemnon arrived home much quicker, albeit encountering stormy seas the entire way. While he makes it home, he is swiftly murdered by his wife, Clytemnestra, as vengeance for Agamemnon's murder of their eldest daughter ten years prior. Agamemnon's shade would reappear to Odysseus in the Underworld years later, warning him to return home in disguise lest his wife still harbor her own misgivings.
Odysseus Encounters Polyphemus
Odysseus opted to take a different route home from Menelaus and Agamemnon, planning to stop along the route to restock for supplies as opposed to taking a direct path. After stopping to pillage a town, they are blown off course and find themselves on the island of the Cyclopes, where they encounter the one-eyed monster Polyphemus. After the giant eats several of Odysseus' men, they escape by blinding him, angering Polyphemus' father, the sea god Poseidon, in the process.
Odysseus' Crew is Decimated by the Laestrygonian Giants
Poseidon's rage pushes them off-course once again, and Odysseus and his crew find themselves at Aeaea, where they quickly discover themselves among the Laestrygonian giants. The giant warriors kill the majority of Odysseus' crew, and in the process destroy two of the three ships that made up Odysseus' small flotilla. Odysseus and only a handful of men survive, including his second-in-command, Eurylochus. Tensions mount about Odysseus' ability (or inability) to lead them.
Odysseus' Surviving Crew Runs Afoul of Circe
The men seek refuge and food further along the coast, and after leaving Odysseus to hunt for game with his bow, they approach the dwelling of the witch Circe. Circe invites the men in and feeds them, only to then reshape the crew into pigs. Odysseus discovers her treachery, and convinces her to change the men back so that they can return home. Given her power of sight, Circe warns Odysseus that he can't make it home to Ithaca without first going to the Underworld.
Odysseus Receives Advice in the Underworld
On the shores of the Underworld, Odysseus and his crew meet the shades of several familiar figures, including Agamemnon, Sinon, and the blind prophet Tiresias, each of whome provides a warning and advice to Odysseus. Agememnon tells Odysseus to return home in disguise, Sinon discloses his manipulation at Antinous' hands during the drawing of lots before the Trojan War, and Tiresias alerts him that he will be the only one of his crew to ever return home.
The Sirens, Scylla, and Charybdis
The men sail on and encounter the Sirens, whose song torments and entices men to their doom. While one of the crew is lost, even more are lost when they are forced to choose between the deadly whirlpool Charybdis and the monster Scylla. Despite Odysseus' warnings, they choose to pass by Scylla, and six more crew members are lost to the monster's appetite.
The Last of the Crew Kills Apollo's Cattle
They next land on the island of Thrinacia, where they encounter a herd of cattle that belong to the sun god Apollo while being trapped on the island by strong winds. Once again the crew ignores Odysseus' warning to leave the cattle alone (which Tiresias told him would result in their deaths), and in their extreme hunger they kill and eat one of the steers. The winds die down long enough for them to leave Thrinacia, but the rest of the crew is swiftly killed by an epic storm created by the combined might of Apollo, Zeus, and Poseidon.
Odysseus' Seven-Year Affair with Calypso
Odysseus barely survives the shipwreck, and washes up on the shores of Ogygia, the island where the nymph Calypso has been stranded. In her loneliness, Calypso entraps Odysseus on the island for seven years with the help of a lotus flower that forces Odysseus to forget his past and his desire to go home when he eats it. After seven years, Calypso takes pity on Odysseus as he inquires about his own past, and she recognizes his desire to return home to his family.
It is during the period in which Calypso stops Odysseus from consuming the lotus flowers that he begins to recount his entire journey home, telling the story as he himself remembers it. The events that the audience sees technically are unfolding during long flashbacks that occur as Odysseus tells the story to Calypso. Once he has fully remembered who he is, what he's done, and why he wants to go home, Calypso allows him to build a raft from the wreck of the ship that stranded him there seven years prior. Odysseus embarks on the raft, and fully entrusts himself to the will of the gods after defying them during his entire journey, eventually landing on the shores of Ithaca.
Telemachus Visits Menelaus
Although it's interspersed among the other events of Odysseus' journey, the entire narrative surrounding Penelope, Telemachus, and the suitors plays out in roughly a week, and coincides with the end of the journey. Telemachus journeys to Sparta to consult with Menelaus about his father's whereabouts, and in the time he is gone, Odysseus lands on the island. He discovers from Eumaeus that Telemachus is in danger, as assassins from Antinous' group of suitors aim to murder him along his road home. Odysseus, in disguise as a beggar and Trojan War veteran, helps his son escape the assassins and return home.
Odysseus' Disguised Return Home
Odysseus arrives home with Telemachus and Eumaeus, with the former only recognizing him when Odysseus' faithful hunting dog, Argos, recognizes his master. That leads to the challenge laid out by Penelope at the ending of The Odyssey, and Odysseus' eventual reveal that he has in fact returned to reclaim his home after 20 years. He kills most of the suitors, with the survivors bending a knee to their rightful king, and reunites with his wife. They turn the throne over to Telemachus, and fulfill their dream of sailing away into the west together, although this time with the explicit purpose of Odysseus honoring all his fallen crew and friends that he never got to give proper funeral rights.
The Odyssey condenses some of the stops along Odysseus' journey from Homer's original epic poem for the sake of the movie, and it's clearly the right decision. Despite running almost three hours, Nolan's unique ability to weave stories across time makes it so The Odyssey never feels boring, repetitive, or slow. The epic end to the narrative feels well-earned, especially if you fully appreciate the sheer amount of time that actually passes during the events that come after the fall of Troy and Odysseus' fateful desecration of Zeus' Law.