Thomas Riker was the result of a transporter accident in 2361 that created two William T. Rikers indistinguishable from each other. Eight years later, the USS Enterprise-D discovered Thomas on Nervala IV, the site of the accident, where he had been living in seclusion. Because of this seclusion, Thomas had remained deeply in love with Deanna Troi, and dwelt on the fact that he was unable to meet her on Risa later in the year of the mishap. Troi was reluctant to get involved with Thomas, but he eventually won her over, but when he had to leave the Enterprise-D, her feelings were not strong enough for her to leave with him. Thomas transferred to the USS Gandhi to continue his Starfleet career.
The following year, Thomas expressed dismay at the Federation's policies towards the Demilitarized Zone and joined the Maquis. Early the next year, Thomas posed as William Riker, boarded Deep Space 9 and stole the newly commissioned USS Defiant. With Kira Nerys as his unwilling passenger, Thomas flew to the Orias system where the Maquis believed that the Cardassians were building a fleet of warships. When they arrived, the Defiant was confronted by a fleet of Obsidian Order starships. Thomas surrendered himself to Gul Dukat's forces and received a life imprisonment sentence in a labor camp on Lazon II.