Matthew Harris was an antagonist introduced in the Star Trek: Enterprise episode "Affliction".
He was portrayed by Eric Pierpoint.
In the 2140s Harris was a member of United Earth's Starfleet, working in Security. By the late 2140s he held the rank of Captain. He worked with Malcolm Reed, assigning him to a number of covert missions that made Reed quite uncomfortable. In 2149 the leadership of Starfleet Security began questioning his methods. Harris decided to leave Starfleet before he could be arrested.
At about the same time, Uraei began to recruit personnel to Section 31, and Harris became an operative in the new organization. He again attempted to recruit Reed into the organization prior to the launch of the Enterprise. Reed declined, and that was the last Reed heard of Harris until 2154.
In 2154 Harris began working with contacts in the Klingon Empire, providing them with Augment DNA so they could try to create their own Augments. The Klingon's efforts created a disease that was devastating the Empire. In response Harris helped arrange the kidnapping of Doctor Phlox. He contacted Reed to sabotage the Enterprise and keep them from tracking down Phlox too soon. When discovered Reed was arrested and confined to the brig by Captain Jonathan Archer. Reed was released after confessing what he knew to Harris. After the resolution of the crisis, Harris felt confident that the Empire would no longer bother them for quite a while. He contacted Reed, who told him that the only officer he answered to was Archer, and not to contact him again.
Later that year Reed approached Harris for information on Terra Prime. Harris provided information that allowed the Enterprise crew to find Terra Prime's base on Mars and prevent them from destroying Starfleet Headquarters.
A year later, Reed helped put Trip Tucker in contact with Harris after Tucker felt Starfleet was not doing enough to counter the Romulan threat. Harris brought Tucker into the organization, and helped him fake his death in order to work for Section 31 full time. After the Romulan war and the founding of the Federation, Harris continued to work for Section 31 as it became part of the Federation government.
It was Harris that helped ensure the rise of the Surian tyrant Maltuvis to take over almost all of Sauria. He refused to allow Tucker to stay on Sauria to oppose Maltuvis, leaving the Saurian people to be conquered by a tyrant.
When the Federation faced the Ware crisis, Harris arranged for the Klingons to receive the destruct codes for the Ware. This allowed the Klingons to destroy the Partnership of Civilizations, which had been dependent on the Ware.
After the destruction of the Partnershhip, Tucker came to the conclusion that Section 31 and Harris had to be brought down. Tucker traveled to Sauria to help the resistance against Maltuvis, and to sabotage the Section's plans for Sauria. Meanwhile Archer and Reed helped obtain evidence against Harris and Section 31, and presented it to the JAG.
After the 22nd century version of Section 31 was exposed to the public, Harris and the other senior leadership of 31 fled Earth. They caught up with Tucker near Sauria and then blew up their own ship, hoping to take Tucker with them. Tucker was able to escape via a powerful transporter. With Harris and the rest of the group's biological leaders dead, Uraei laid low, and kept Section 31 disbanded until the time was right to reconstitute it again. The public was not informed of Section 31's actual name in order to keep it from seeming that 31 was sanctioned by the Federation. Instead, the 22nd century organization went in to the history books as The Harris Conspiracy.