3 Nephi opens with catastrophe: a violent storm of fire, earthquake and darkness that the text describes as accompanying Christ's crucifixion in Jerusalem, destroying several Nephite cities and killing many of their inhabitants. Out of that destruction a voice is heard identifying itself as Jesus Christ, and the survivors gather at the temple in the land of Bountiful, where the text describes the resurrected Christ personally descending to teach and minister among them.
This visit is the narrative and theological center of the entire Book of Mormon within Latter-day Saint reading. Christ is described healing the sick, blessing children individually, instituting the sacrament, and teaching at length, and the text presents these events as a direct extension of his ministry beyond the biblical narrative rather than a separate or competing revelation. He organizes twelve disciples among the Nephites, parallel to the twelve apostles of the gospels, and the book describes a following period of continued visitation and instruction before he departs, promising to return.
Because the visit is presented as a literal historical event within the Book of Mormon's narrative frame, it functions differently from a vision or a prophecy elsewhere in the text: the whole community is described as witnessing it together, which the tradition treats as the strongest possible form of testimony the record offers.