2 Thessalonians 2:2-4
That ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that the day of Christ is at hand. Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition; Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God.
God told us that there was going to be a time when the people of this earth would fall away from the truth. This has happened already. When the angel came to Joseph Smith and restored the true gospel back on earth this was completed. Up to that point and time, the truth was lost to mankind. Now with the messenger coming back we are able keep the truth alive. Will you follow the truth?