Missing Link is a two-part fan-fiction story by the pseudonymous Ln X.
In 2393, an official of the Department of Temporal Investigations presents to the command staff at Deep Space 9 a Cardassian data rod that seems to be nearly 350 years old, though it was manufactured in 2393. Once decrypted by Max Weatherly, a DS9 officer, it is shown that the rod contains a recording from Weatherly's ancestor, a 21st century physicist whose work may have been the basis for Zefram Cochrane's development of the warp drive.
A team from DS9 is sent back to 2053 Earth to ascertain the truth, and to ensure that their timeline is preserved.