Scott Miller (Tam Williams) is a second year psychology student at the University of the South Downs. He shares a house with Joe Hunter (Paul Bettany), a second year law student, and Susie Selby (Emily Woof), Joe'S girlfriend who is a nurse at the local hospital.
Scott, who is very into computers and a bit of a net head, is preparing a psychological experiment as part of his course, based on Milgram's work in the 60's. Using a mock-electric chair, he plans to see how much pain people are prepared to inflict on others in a controlled environment. Other students will be brought in as participants.
Joe is unfaithful to Susie. She doesn't know it but he still plays the field whereas Scott is looking for a more challenging, meaningful relationship. Escaping to the local Internet café to avoid Joe'S attempts to get him off with the pneumatic Mandy, Scott meets Charlie (Cathy Brolly) aka Rich Bitch in an active world. When they meet in real life, it seems as if his dreams have come true. She is tough, sexy and very bright, also into computers, especially on-line porn which she introduces Scott to.
Charlie is trouble. Susie can't stand her, Scott becomes obsessed and stops going in to college but neither of them know that Joe and Charlie have met each other before. Charlie plays a cat and mouse game with Scott, disappearing and then reappearing with no explanations. She tells Scott that a local DJ, Brent Moyer (Jason Orange) means nothing to her but he is obviously supplying her with drugs. Charlie moves in with Scott. One night, Joe finds Charlie naked in the bathroom. They have sex and Charlie is gone by the time Scott wakes up the next day. Scott goes round to the DJ's house. Charlie is there but she won't speak to him. Very depressed, Scott takes to his room where he retreats into a world of on line pornography. By this time he has upgraded his equipment, installing and MPEG card and a sound card so he can talk to prostitutes live. One of them, Sadie, offers to sell Scott a limited edition cd rom. He gives her his credit card details and waits for "KILLER NET" to arrive.
Charlie seems to have disappeared and Scott returns to his classes after a few days absence, determined to catch up. That evening he finds a package waiting for him. The cd rom, KILLER NET has arrived from America.
While Carol from the art department works on his false electric chair, Scott's studies are once again forgotten as he becomes immersed in his new computer game. KILLER NET invites the player to select one of three locations to play a murder game. Scott chooses Brighton. Using existing streets and actual film footage, the player is invited to choose a victim to stalk, kill, dispose of the body and avoid police detection. Scott discovers the actual streets where KILLER NET is set and he stakes out the house where his "victim" lives, tracing her route to work in a shoe shop which also exists. Joe and Susie become involved, making suggestions about choice of weapons, best method of disposal etc.
Unknown to either Susie or Scott, Joe is seeing Charlie. Scott achieves a very high score and successfully completes the game. The game then invites him to insert his own choice of victim, not one of the girls already programmed. But Susie is bored of the game and the three flatmates go out to Laser Quest.
Scott is unprepared to see Charlie in Laser Quest but his hurt is soon forgotten as he suggests they all go clubbing. Once in the club, Scruffy (Simon Meacock) another student, warns Scott that Charlie or Rich Bitch as she is known on-line, has flamed him - humiliated him on the internet. Scott and Charlie have a row and Scott goes to the Techno Cafe to read what she has written. He is mortified and proceeds to get very drunk. Thrown out of the Cafe, Scott gets a taxi, throws up in it and eventually gets home. In a drunken state he inserts Charlie's name and address as his latest "victim" in KILLER NET. The next morning, a very hungover Scott heads home to see his parents. Later that day, a real body is discovered at one of the disposal sites specified in KILLER NET.
Mr Miller receives Scott's credit card bill for over a thousand pounds and gives him a bollocking. Scott returns to university determined to pull his socks up.
It's now the DJ's turn to go round to Scott's house, looking for Charlie. Apart from anything else, he thinks she's stolen his wallet. There is a bit of a scuffle and Scott ends up with a black eye. Forensics are unable to identify the body of Heather Ringwall aka Charlie and a police notice is circulated. The response leads the police to the DJ Brent Moyer, who identifies the body as Heather Ringwall - Charlie.
When Brent remembers Charlie had some aggro with Scott, DI Colby is sent to the university where Scott is in the middle of his experiment. Scott recognises Colby from the game and thinks Joe has sent him as a wind-up. When he is told Charlie is dead, Scott freaks, tries to run for it and is arrested. During a search of Scott's house the police discover the cd rom hidden amongst Scott's books on killing, bundled up in a black sack. It looks like Joe was trying to get rid of everything to protect Scott. Susie also discovers a wallet full of money and a photo of Charlie and Brent hidden in the wardrobe in her bedroom.
All Scott's computer equipment is at the police station where he is being held. A computer expert is called in and Scott shows him and the police officers how he played the game, in an attempt to explain why he ran. Yes, he killed her in the game, but not in real life! When Scott inserted Charlie in the game, he only played as far as the disposal stage and did not complete the whole game, he therefore did not achieve a perfect kill. When he shows the police how the game is played, he repeats exactly what he did with Tracy. Although the game allows you to enter your own victim, it cannot create a new scenario. The new character "fits over" the original. Consequently, when Scott plays right the way through and achieves a perfect kill with Charlie, she too is erased from the game and the player able to insert another of their own victims. Despite the fact the computer expert Greg suggests they could re-enter Charlie's details, they decide to input a fresh set of details to see if Scott is telling the truth. WPC Pam Boxer volunteers.
Robin Butler-Cook arrives in Brighton and opens up his warehouse. Inside are several high-powered computers and some recognisable props from Killer Net. He starts his computer and brings up a file entitled Libra. We see the identikit picture of Charlie along with her details.
When Susie takes the wallet she found round to the DJ's house, Robin is waiting outside the front door. He greets her as Charlie and rushes off when she tells him that Charlie is dead. Robin returns to his warehouse with a copy of the local newspaper which reports on Charlie's murder. We see him draw a list of question marks down the side of the paper. Robin's computer starts to bleep as the details of a new LIBRA victim are fed through, those of WPC Pam Boxer.
Back at the police station, Greg notices the modem light is flashing. A message is being sent out, or someone is sending one in, but who? When Colby rushes to tell Collingwood he thinks there is something very sinister about the game and that Scott has probably got himself into something he doesn't understand, Collingwood confronts him with some recently arrived forensic results. The hammer that was taken from Scott's house has traces of Charlie's blood on it.
The police have been granted a court order to keep Scott in custody for three more days. Collingwood goes to interview the university students who were at the Chamber club on the night Charlie was killed and learns from Scruffy that Charlie flamed Scott. Joe denies playing the game.
Colby is not convinced that Scott is their man. He is more worried about the game and thinks that the girls may be murder victims in real life. In order to test this theory, he goes to visit the house that was featured on the game, Tracy's house. The landlady tells him Alison Jackson used to live there but disappeared about nine months ago, leaving her stuff behind. Old photographs confirm that Alison was Tracy in KILLER NET, although when Colby later asks Boxer to put a trace on her it turns out she is alive and working as a stripogram girl. WPC Boxer is unaware that Robin is filming her. He is also filming her house and has installed a hidden camera.
While Scott is trying to find Sadie to show the police how he got hold of KILLNER NETin the first place, Colby is interviewing Susie. She has discovered that Charlie had been using her credit card and ran up a massive bill. It is all getting too much for her and she tells him that she didn't go home with Joe that Saturday night. She also tells him that she found Brent's wallet. Back at the station, an email message appears on Scott's computer: "Charlotte Thorpe was mine, the Libra kill is always mine", signed Dome.
With the arrival of Colby especially when Scott tells Collingwood that he and Joe had played the game together and JOE suggested using the hammer. Joe is further implicated when security footage from the Chamber Club shows that he was at the club with Charlie long after Scott had left. Joe is picked up for questioning.
Colby is still convinced that they should find out more about the game. Boxer is able to trace Royston Burrows, the actor who played Dome, who remembers the man who made the film as being humourless and obsessive about computer games. Colby promises to buy Pam Boxer dinner.
A series of leads takes Colby to the home of Justin Holloway, who tells Colby that Robin Butler-Cook used to design games for him but was imprisoned for computer fraud after hacking into the BCCI bank. He also tells him he thinks Robin had a warehouse somewhere outside Brighton. Colby comes away with a company brochure showing an old photograph of Robin.
Joe breaks down under questioning and admits that he was at University with Charlie in Dublin. They had been involved in heroin dealing. When they got busted, Charlie was sent to prison but no-one else was implicated. As the noose tightens around Joe'S neck, Joe reveals that Charlie came to Brighton to get back at him for dumping her. Joe had a career and a future to protect, he couldn't let her ruin his chances. He confesses to killing Charlie saying that the game gave him the perfect murder plan.
Colby visits some industrial estates and discovers Robin's warehouse. It is empty apart from a photograph of the Old Pier, taped to the door, as if deliberately placed to be seen. Cutting back to Pam Boxer's flat we see her pick up a hand delivered postcard of the Old Pier, seemingly from Colby with a message to meet him there. As she leaves the flat, the phone rings and Pam comes back in just in time to hear the end of Colby's message, "We can eat Chinese or Indian". She didn't hear the first part of the message which asked her to check out the disposal sites in Killer Net but made no mention of meeting at the Old Pier.
Back at the police station, the incident room is quiet. Only Hawkes and Nathan are there to take delivery of a package addressed to Colby and The Tunnel Murder Team. It is a video of all Robin's footage of Pam Boxer.
Colby goes round to Scott's house to show Susie the photo of Robin from the brochure. She recognises him as the man who thought she was Charlie, outside Brent's flat. Despite the fact that Joe has admitted to killing Charlie, Colby has a hunch that Robin was using the Killer Net game to provide him with victims when players entered the details of their own choice, the Libra option. The game encourages players to enter their own victims - remember the flashing modem light when new details were entered, remember the email? Suddenly he realises that Boxer could be in terrible danger.
Colby, rushes round to Pam's flat only to find Collingwood, Hawkes and Nathan coming out. Robin has obviously been taunting them and Colby realises the photo of The Old Pier was a clue. Sure enough, that is where they find Pam Boxer, horribly mutilated, strung up between racks of old puppets in the old theatre on the pier, a video camera silently whirring. Collingwood now realises that Colby was right about the game. They send out an all ports warning to apprehend Robin Butler-Cook. A supremely confident and closely shaven Robin is approaching the airport check-in behind his doppleganger, who is lank haired and wearing glasses. As the bogus Robin is stopped and arrested, the real Robin slips through under an assumed name, they have missed him!