Cassandra Spender (played by Veronica Cartwright) was a repeater, or a multiple abductee, critical to the plans of the Syndicate. She was the ex-wife of the Cigarette Smoking Man and mother of Special Agent Jeffrey Spender, as well as "Patient X," the primary test subject in the project to develop an alien/human hybrid.
Spender was returned and abducted multiple times, but found no one believed her account of her abductions. This became very disparaging and she almost considered taking her own life. In 1995, however, she learned of Agent Fox Mulder, someone who investigated similar cases, and believed he must believe her. However, she would not get the chance to talk to him for awhile. (TXF: "Patient X")
In 1998, Spender would gain some attention while proclaiming her belief that the aliens were coming to promote peace. A video of her doing so was part of a visiting lecturer panel at MIT. Agent Mulder was part of this panel, however, at the time, he was disillusioned by the revelations of Michael Kritschgau. He did not believe Spender's insistence that the aliens were calling her and other abductees to "lighthouses," where colonization would begin, despite a mass incineration of abductees at Skyland Mountain, where Scully had been abducted three years earlier.
A rebel group of aliens who mutilated themselves to avoid infection by the black oil were attempting to destroy the work the Syndicate had done, finally summoning both Scully and Cassandra Spender to the same site in Pennsylvania. Before the rebels could manage to destroy the group, however, an alien craft appeared overhead and abducted Cassandra. (TXF: "Patient X", "The Red and the Black")
Cassandra had come to believe that, while the aliens had cured her of her former disabilities, they had far more sinister motives than she had originally thought, having learned of their plans for colonization. Cassandra was brought later to a train car in the Potomac Yard, Virginia. There, Syndicate doctors examined her and determined she had successfully become a hybrid. However, during the examination the doctors were burned alive by the faceless rebel aliens. She had been spared in order to expose the alien conspiracy, knowing that she would be examined by more doctors not in the Syndicate.
Jeffrey soon came to her and made sure she was OK, but Cassandra insisted to see Agent Mulder in order to explain her newfound concerns. Cassandra was kept in the hospital and was visited by Scully again, which she very much enjoyed, though also asked her where Mulder was. She later decided to escape the hospital and made it to Mulder's apartment, where Scully and Mulder were. Cassandra quickly tried to explain and plead with Mulder to kill her in order to stop colonization. Mulder finally believed and drew his gun just as someone was pounding on the door. (TXF: "Two Fathers") It was a decontamination team from the CDC led by Diana Fowley sent to capture her for her presentation to the alien colonists. She was brought to Fort Marlene Decontamination Center and separated from Mulder and Scully. There, her son came to her and explained he was trying to keep her safe, but Cassandra was just disappointed he did not believe or understand. The CSM came to her to escort her with the doctors to El Rico Air Force Base. She pleaded with him to kill her as well, but he could not. When she arrived at the base's hangar, the rest of the Syndicate was present. However, the meeting started early, having been orchestrated by the alien rebels. They killed the Syndicate members and Cassandra. (TXF: "One Son")
After utilizing Nazi technology in transgenic implantation and UFO technology salvaged from the 1947 Roswell crash, humans in the Syndicate contacted the aliens to offer assistance in plans for colonization, what the Cigarette-Smoking Man called the "perfect conspiracy." They offered to develop a race of alien/human hybrids to assist in the colonization through their genetic work, which they soon realized would be a slave race. Members of the conspirators' families were given to the aliens in exchange for access to an alien fetus, which was kept in cryogenic storage. (TXF: "The Erlenmeyer Flask") The original exchange took place at El Rico AFB in November of 1973. Many of the abductees were returned for subsequent testing, including Cassandra and Jeffrey Spender, and the reluctantly-included Samantha Mulder. With the genetic information obtained through these experiments, the Syndicate hoped to forestall the invasion while they worked slowly on the project, and, in secret, possibly develop a vaccine which would prevent the possession—or incubation—of victims infected by the alien virus.
Beginning with the 1973 abductions, Cassandra was taken many more times, each time being subjected to further and further tests, originally disabling and finally curing her. It was revealed that she was the primary test subject, and became, shortly before seeing her doctors attacked, the first successful living human to be hybridized with alien genetics. Upon learning of a successful hybrid, the colonists would have taken steps to eliminate the evidence of the project, but the gathering to present her to the colonists — a show of support that might buy slightly more time — was infiltrated by the faceless rebels, who destroyed Cassandra and the elders but failed to eliminate the Cigarette-Smoking Man or other factions of the Syndicate.
- The X-Files