Tenn. Code Ann. § 21-1-404

The original defendant, or the defendant's heir, representative or assignee claiming under the defendant by virtue of any act done before the commencement of the suit, may, within six (6) months after service of a copy of the decree, or within three (3) years after the decree, be admitted to answer the bill, upon petition showing merits, and giving security for the payment of costs, and witnesses on both sides may be examined, and such other proceedings may be had on the suit as if the cause were then newly begun.