Despite being one of the earliest and most important contributors to the restoration in late 1837, Martin Harris was cut off from the church for associating with a group that was undermining Joseph Smith and church leaders for the next several years. Martin was in and out of the church and had joined other religious groups as well, including the Shakers and an LDS offshoot led by James Strang. Remarkably, he persistently continued to testify of the Book of Mormon during all this time. By the late 60s, Martin was isolated and languishing in Kirtland.
Earlier, he had remarried, but his wife and children had left and gone to Utah. Eventually, his ever burning testimony of the Book of Mormon, coupled together with his desire to see his family again, compelled him to come out to Utah and reunite with the church. Encouraged and assisted by some homebound missionaries, Martin then made an honorable return to Utah and was rebaptized on September 17th, 1870, at the age of 87 in his final days, even as he was ill and approaching death.
He was constantly bearing testimony whenever he had sufficient strength to do so. Moments before his death, he assured those attending to him at his bedside. Yes, I did see the plates on which the Book of Mormon was written. I did see the angel. I did hear the voice of God. And I do know that Joseph Smith is a prophet of God. And now you know why.