"A Spider in the Web" is an episode from the second season of the science-fiction television series Babylon 5.
An old friend of Talia Winters, Taro Isogi, is on Babylon 5 to conduct negotiations with various large corporations on pushing through reforms on Mars colony. His negotiations have caught the eye of the Earth Alliance Senate, who fear he is negotiating financing to conduct a new Mars rebellion. At the same time, a mysterious group operating out of the San Diego Wastelands also sets a plan into motion, culminating with a cargo container opening on Babylon 5, and a figure stepping out.
After an initial negotiation session, Talia and Taro are approached in a corridor by Abel Horn, who yells "Free Mars!" and electrocutes Taro. When he goes to attack Talia, she scans his mind, picking up memories of him in a fighter exploding while attacking an Earth Alliance cruiser. After the scan, Horn moves on, seemingly unaware of Talia's presence. Talia is interviewed by Captain Sheridan, who attempts to understand the images. It is revealed that Talia has scanned numerous members of the Free Mars movement, who she describes as violent fanatics with a hatred for Earth. Talia believes that this person is different, as there was no emotion of any kind in his mind, and there is more going on that people realize.
A short time later, Abel Horn uses a StellarCom station giving it a seeming invalid code, only for the screen to change to one shown at the mysterious group's head quarters. He reveals phase one is complete, and downloads his record of the encounter with Isogi. His control officer identifies Winters and, deeming her a potential threat to the mission, orders Horn to eliminate her before proceeding to phase 2.
In the course of his investigation, Sheridan learns that Isogi's plan was create a free and independent Mars, without bloodshed, and beneficial to all parties. Amanda Carter, a Mars government official who Isogi was negotiating with, speculates that both the Earth Alliance Senate and the Mars Conglomerate would want him dead. Garibaldi also informs him that there would be no way for the killer to get his electrocution weapon on to the station undetected unless he had special help.
Horn soon corners Talia on a walk way, kills her security escort and prepares to kill her the same way he did Isogi. Before he can strike, Talia again picks up the images in his head, and is able to escape while he is distracted. For a brief time he appears to be normal, wondering what "they" did to him, before returning to a rigid state (revealing that some method of brain-washing may be at work). Talia again seeks out Sheridan and tries to explain what she saw in her attackers head, this time in a bit more detail. Based on Talia's description, Garibaldi is able to identify Horn who was a leader of revolutionary group Free Mars. However, according to EarthForce records Horn was killed in an encounter with an EarthForce warship in orbit of the Martian moon Phobos. Talia realizes that this is what she has been seeing and reveals that the images in Abel's head are actually of his death. Sheridan also recognizes Horn; he was responsible for a terrorist attack in which friends of John and his late wife Anna were killed.
Horn seeks out Amanda Carter, who he calls "Commander", revealing that he was rescued from the wreckage of his craft and fixed up by a "snake head doc". He claims to have come to Babylon 5 once he learned she would be there, but has no memory of killing Isogi. He tries to blackmail Carter to get him smuggled back to Mars, in exchange for keeping her involvement in Free Mars secret. After a brief breakdown to his normal persona, Horn returns to his normal state and attacks her.
Sheridan recalls details of a project codenamed Lazarus, an Earth Force cyber experiment from the 2230s which sounds similar to what Talia described regarding Horn. Further research, using the computer, reveals that it involved using subjects on the verge of death and hardwiring their brain with a computer intelligence. Telepaths would focus the mind of the subject on the moment of death, shutting out all other conscious thought, with the computer taking complete control over the body. He speculates that Horn is the result of this project, and that Talia's mind scans are causing problems with his programming.
Carter, at Horn's insistence, contacts Talia and requests they continue the negotiations Isogi had begun. Talia travels to Carter's quarters for a meeting, and is attacked by Horn when she arrives, who wants to know what he has become. Talia again scans his mind, seeing his death, and then recovery by human doctors and a Psi-Cop. He takes Talia hostage upon the arrival of Sheridan and Garibaldi (with Zack Allen in the background in his first appearance), but is almost persuaded to give up before his programming regains control. After being wounded Horn initiates a self-destruct, blowing himself up, eliminating all of Sheridan's evidence.
When discussing the images she pulled from Horn's mind with Sheridan and Garibaldi, Talia does not inform them of the Psi-Cop's presence. Sheridan also reveals that he is an avid collector of information of black projects and secret organizations. He says that he has been tracking a rogue agency within EarthGov for six years named Bureau 13. He blames them for Horn's programming, but knows he cannot prove anything. He states his desire to kill this "spider in the web".
In her quarters, Talia scans through the listing of Psi-Cops looking to identify the one from Horn's memories, and discovers that she is dead. Meanwhile, the same Psi-Cop is shown in the Bureau 13's headquarters in San Diego receiving news of Horn's partial failure.