In the poem's first line, we meet its protagonist, "an ancient Mariner." He stops one of three people on their way to a wedding celebration. The leader of the group, the Wedding Guest, tries to resist being stopped by the strange old man with the "long grey beard and glittering eye." He explains that he is on his way to enjoy the wedding merriment; he is the closest living relative to the groom, and the festivities have already begun. Still, the Ancient Mariner takes his hand and begins his story. The Wedding Guest has no choice but to sit down on a rock to listen.
The Ancient Mariner explains that one clear and bright day, he set out sail on a ship full of happy seamen. They sailed along smoothly until they reached the equator. Suddenly, the sounds of the wedding interrupt the Ancient Mariner's story. The Wedding Guest beats his chest impatiently as the blushing bride enters the reception hall and music plays. However, he is compelled to continue listening to the Ancient Mariner, who goes on with his tale. As soon as the ship reached the equator, a terrible storm hit and forced the ship southwards. The wind blew with such force that the ship pitched down in the surf as though it were fleeing an enemy. Then the sailors reached a calm patch of sea that was "wondrous cold", full of snow and glistening green icebergs as tall as the ship's mast. The sailors were the only living things in this frightening, enclosed world where the ice made terrible groaning sounds that echoed all around. Finally, an Albatross emerged from the mist, and the sailors revered it as a sign of good luck, as though it were a "Christian soul" sent by God to save them. No sooner than the sailors fed the Albatross did the ice break apart, allowing the captain to steer out of the freezing world. The wind picked up again, and continued for nine days. All the while, the Albatross followed the ship, ate the food the sailors gave it, and played with them. At this point, the Wedding Guest notices that the Ancient Mariner looks at once grave and crazed. He exclaims: "God save thee, ancient Mariner! / From the fiends that plague thee thus!- / Why lookst thou so?" The Ancient Mariner responds that he shot the Albatross with his crossbow.
In editions where it is included, the Latin epigraph serves as a semi-thesis for the poem. It is a Latin quote from Burnet's "Archaeologiae Philosophicae" (1692), which Coleridge translates as follows:
I readily believe that there are more invisible than visible Natures in the universe. But who will explain for us the family of all these beings, and the ranks and relations and distinguishing features and functions of each? What do they do? What places do they inhabit? The human mind has always sought the knowledge of these things, but never attained it. Meanwhile I do not deny that it is helpful sometimes to contemplate in the mind, as on a tablet, the image of a greater and better world, lest the intellect, habituated to the petty things of daily life, narrow itself and sink wholly into trivial thoughts. But at the same time we must be watchful for the truth and keep a sense of proportion, so that we may distinguish the certain from the uncertain, day from night.
Burnet, who authored the original quote, begins by acknowledging that "invisible natures" such as spirits, ghosts, and angels exist; moreover, there are more of them than their readily-perceivable counterparts such as humans and animals. However, "invisible natures" are difficult to classify, because people perceive them only occasionally. Burnet asserts that while it is important to strive to understand the ethereal and ideal, one must stay grounded in the temporal, imperfect world. By maintaining a balance between these two worlds, one avoids becoming too idealistic or too hopeless, and can eventually reach the truth. By prefacing "The Rime of the Ancient Mariner" with this quote, Coleridge asks the reader to pay careful attention to the near-constant interactions between the spiritual and temporal worlds in the poem. Like the Ancient Mariner, the reader must navigate these interactions and worlds in order to understand the truth ingrained in the poem. The Ancient Mariner as a character can be identified with a number of archetypes: the wise man, the writer, the traitor, and more. The epigraph suggests that regardless of with whom the reader associates the Ancient Mariner, there is great importance in the way in which he manages (or fails) to balance the spiritual and temporal worlds.
From the Ancient Mariner's first interaction with the Wedding Guest, we know there is more to him than the fact that he appears unnaturally old. He has a "glittering eye" that immediately unnerves the Wedding Guest, who presumes he is mad and calls him a "grey-beard loon." Yet there is more to his "glittering eye" than mere madness, as he is able to compel the Wedding Guest to listen to his story with the fascination of a three-year-old child. Although he is clearly human, the Ancient Mariner seems to have a touch of the otherworldly in him.
Throughout Part 1, the temporal world interjects itself into the storytelling haze in which the Ancient Mariner captures the Wedding Guest and reader. For example, just as the Ancient Mariner begins his tale, the joyful sound of a bassoon at the wedding reception distracts the Wedding Guest. He "beat[s] his breast" in frustration that he is missing the festivities. In light of Burnet's quote, one can say that the temporal world with its "petty" pleasures tempts the Wedding Guest. He is of that world - indeed he is next of kin to the bridegroom and therefore intimate with the festival's worldly joy. Meanwhile, the Ancient Mariner cannot enjoy the temporal world because he is condemned to perpetually relive the story of his past.
In the Ancient Mariner's story itself, the spiritual and temporal worlds are confounded the moment the sailors cross the equator. Suddenly the natural world - which is closely connected to the spiritual world - makes the sailors lose control of their course. The storm drives them into an icy world that is called "the land of mist and snow" throughout the rest of the poem. The word "rime" can mean "ice", and can also be interpreted as an alternate spelling of the word "rhyme." Therefore, as much as the poem is the rhymed story of the Ancient Mariner, it is also the tale of the "land of mist and snow": the "rime", where the Ancient Mariner's troubles begin. By calling the poem "The Rime of the Ancient Mariner," Coleridge equates the "rhyme" or tale with the actual "rime" or icy world. As we learn at the story's end, the Ancient Mariner is condemned to feel perpetual pangs of terror that force him to tell his "rhyme," a fate just as confining and terrifying as the "rime" itself is initially for the sailors.