"The Ghost Network" is the third episode of the first season of the American science fiction drama television series Fringe. The episode was written by co-executive producer David H. Goodman and supervising producer J. R. Orci, and was directed by Frederick E. O. Toye. The episode follows the Fringe team's investigation into a bus that was filled with amber, encasing the people inside. They discover a man named Roy (Zak Orth) who predicted it and other similar events, and Walter realizes Roy has connections to a past experiment he did over twenty years ago, called the "Ghost Network".

The episode was important in the show's evolution, as the writers noted that Roy was the first guest character the audience could get emotionally invested in. "The Ghost Network" also included their quest to explain seemingly impossible and weird phenomena through a real scientific explanation from Walter's past research.

It first aired on the Fox network in the United States on September 23, 2008. An estimated 9.42 million viewers watched the episode on its first broadcast. It received mixed reviews, with many believing the show to be finally finding its legs, while others worried over the ongoing formulaic storylines featured in each episode.

A man named Roy McComb (Zak Orth) confesses to his priest that he sees visions of bad things, including a bus where everyone is going to die. Simultaneously with this scene, a man enters a bus, unleashes a canister emitting gaseous fumes, and steals a backpack before quickly getting off. The Fringe team arrives soon after, only to find the fumes have hardened into an amber-like substance, trapping and killing those inside. Walter (John Noble) studies the substance and concludes it started out as a gas and then solidified, suffocating the passengers. While looking at a victim's video footage, Olivia (Anna Torv) discovers a backpack is missing, and traces it back to one of the victims, a Federal employee with undercover connections to a drug cartel. They interview her "handler", who comes to identify her body. The Fringe team finds out about Roy, and search through his apartment, believing he is behind the bus and other Pattern-related terror attacks. They soon realize all of his drawings are dated before the incidents took place, despite the fact that several of them were never made public. In an interrogation, Roy tells Charlie (Kirk Acevedo) he's been receiving his visions for nine months, roughly when they began seeing Pattern-related attacks.

Meanwhile, they trace the substance to Massive Dynamic. Olivia interviews Massive Dynamic executive Nina Sharp (Blair Brown), who tells her the substance has been seen in an attack before. Walter suspects Roy is psychic and runs tests on him before realizing Roy has some kind of magnetic compound in his blood. This leads Walter to recall he and his old lab partner William Bell had conducted research on creating a "Ghost Network" to secretly communicate messages from one person to another in an otherwise undetectable frequency range. During this research, Roy was one of his past test subjects. Walter further theorizes that someone else has perfected his research, and that Roy is overhearing secret messages from some of the people behind the terrorist attacks. Olivia and Peter (Joshua Jackson) arrive at his old house to find equipment needed to tap into Roy's mind.

Using the equipment, they are able to intercept messages in Latin detailing an upcoming exchange at South Station in an hour. They realize the handler removed a small crystalline disk from the Federal agent's hand when he identified her body, and that he is now going to exchange it for something else. Olivia intercepts the man, who is killed before she can talk to him. She chases another man involved in the exchange, who commits suicide in front of a bus after giving them a briefcase containing the disc. Phillip Broyles (Lance Reddick) secretly gives the disc to Nina for analysis, while Roy is sent home, as they believe he will no longer see visions because the Ghost Network has been compromised.

Executive producer Jeff Pinkner decided he wanted fellow executive producer David H. Goodman and supervising producer J. R. Orci to collaborate in writing the episode; Goodman wrote the first half, while Orci wrote the rest of the episode. The two later worked together on only one other episode, "The Equation". Frederick E. O. Toye directed the episode, as he had worked previously with the writers on Alias. The writers had the idea for a couple of weeks of Olivia walking into an apartment and discovering walls covered with drawings of events that "no man could possibly have known about". They wanted to take "urban myths or legends of strange events" and come up with a fringe science equivalent; this led them to creating the story of Roy, a man with seemingly "psychic" abilities, which they then expanded by offering a real scientific explanation in the form of Walter's past research. In the show's early development, the producers were also unsure about how other aspects should be developed, such as Joshua Jackson's character Peter. For instance, in "The Ghost Network", they debated whether or not Peter would break into his childhood home before finally "stalling and just let him do it"; Orci came up with Peter's explanation to Olivia, that he used to live there so it wasn't really breaking in.

The character Roy McComb was played by actor Zak Orth. Roy's name was inspired from Richard Dreyfuss' character Roy Neary in Close Encounters of the Third Kind. The writers noted in the audio commentary that Roy was the first guest character the audience could get emotionally invested in. They wanted the actor to shave off his hair in preparation for the experimentation scene in Walter's lab, but Orth successfully "begged" them to change their minds. When casting for the part of Grant, the writers looked for a man similar in appearance to previous character John Scott (Mark Valley), as they wanted "to play into whatever Olivia's feelings about how she was or was not betrayed by John". Peter Hermann won the part.