Sarah calls a taxi to take her to Heathrow Airport, but finds two waiting for her. The first driver intends to charge her extra for making him wait and tells the second driver, a man with an Indian accent, to sod off back where he came from. Sarah decides to take the Indian’s cab rather than the lout’s, but soon realises she’s made a mistake when the driver sees through her claim to be a PR consultant named Lila Quest, claiming that he is her biggest fan. The driver enthuses over her past successes until Sarah, fed up, threatens to set off her rape alarm if he doesn’t shut up. Apparently hurt, he promises to make less comments, and she corrects him -- it’s “fewer,” not “less.” The rest of the trip is spent in relative silence, but the intrusion into her privacy leaves her fuming, and when she arrives at Heathrow the only tip she gives the driver is “mirror, signal, manoeuvre as you drive away.”
Later, Sarah checks her voice mail again and finds another message from Natalie, but deletes it without responding. Sarah’s own journey takes her to the Lakshadweep islands, where she is eventually found trying and failing to get information out of a local malmi, fisherman. Sarah has tried speaking in Malayalam, though not Mahl, and has now resorted to English, but the malmi remains silent, presumably waiting until she offers him a bribe. Her questions about odd goings-on in the 1940s attract the attention of Wendy Jennings, a reporter from Planet 3 who recognises Sarah and offers to compare notes on their presumably related stories; however, it seems that Wendy is being followed by a tall European man, and Wendy thus arranges to meet Sarah that night at a nearby restaurant to talk in private.
Sarah finds it a relief to speak with a fellow journalist who understands what it’s like to be on the move constantly; she hasn’t even unpacked her belongings in her new house yet, including some broken electronic equipment which she can’t repair because they don’t make the parts for it yet. She covers up this slip, and Wendy goes on to explain that she’s investigating the company Scala. Scala is allegedly conducting genetic research to clear a parasitic infection out of certain major Indian lakes, but Wendy has found a connection between Scala and a scandal involving genetically engineered factory farm salmon in Scotland. One of Scala’s researchers, is staying near the tourist resort on Bangaram Island, and Wendy has come to Lakshadweep to interview him. Before she can explain further, she spots the European man from the boat, and slips away, arranging to meet Sarah at Bangaram on Friday evening.
Natalie leaves another message on Sarah’s voice mail, and then calls up Josh while she hacks into the public records office on Sarah’s behalf to look up information on Operation Halter. Josh is at Sarah’s new flat, unpacking for her, and wonders if moving into her dead friend’s flat means Sarah’s getting less paranoid. Natalie reminds him that doesn’t necessarily mean less people are looking for her, but Josh corrects her, just as Sarah would -- it’s “fewer” people, not “less.” Natalie then finds the Operation Halter documentation, but just as she realises that it’s all about to be made public anyway, Josh answers the ringing doorbell -- and on the other end of the line, Natalie hears the sound of Josh being savagely beaten. Sarah’s new apartment is being burgled.
As Sarah and Wendy walk on the beach, admiring the vista of the Chagos Islands, Wendy tells Sarah more about Joseph Brandt, the researcher they’ve come to interview. Their discussion is interrupted when a Jeep churns its way across the wet sand, heading right for them, but Sarah tricks the driver into spinning into the sea, where the cold water cracks his Jeep’s engine block. As she and Wendy retreat to their hire car, she realises that the driver was swerving to hit her, not Wendy. Wendy identifies the driver as their stalker and borrows Sarah’s mobile phone so she can call and warn Brandt. However, Sarah refuses to let her call the police; the fewer people they involve, the better. She finally admits that she came to Lakshadweep on the trail of British germ warfare experiments from the late 1940s, in which Brandt was involved. She’s not interested in Scala; she’s interested in Operation Halter.
Josh is in the hospital with a black eye and a broken wrist; fortunately, the thieves weren’t killers, and they just wanted him out of the way while they went about their business. There were two men; one thug who stood guard over Josh, and a smaller Indian man who ransacked the flat. They took one of Sarah’s packing crates, containing a small grey box like a TV or radio with two aerials on top. Natalie managed to get an ambulance to the flat eventually, but was delayed by having to find out where the flat was exactly. If Sarah had told Natalie where she was living, Natalie could have gotten help to Josh more quickly, and Natalie intends to tell her just what she thinks of that; the next time Sarah calls in to check her voice mail, Nat will be connected, and she’ll find out what phone Sarah is calling from.
Sarah and Wendy keep their appointment with Brandt, who has already guessed what Sarah wants to talk about and offers to tell her everything. Operation Halter was a shambles from the start. Many test animals proved unsuitable and were therefore shot and dumped in the sea; the rhesus monkeys had to be treated for pneumonia before they could be infected with the test bacteria; weather conditions proved rougher than expected, and the tests were therefore run off shore in the local fishing grounds rather than in the open sea; and one of the young researchers was himself infected. Brandt also informs Sarah and Wendy that he’s resigned from his position in disgust at what Scala had planned for the Parambikulam-Aliyar project, but before Sarah can find out what he means, there is a knock at the door. Wendy lets in a police officer, and too late, Sarah recognises him as their stalker. The man struggles with Brandt and a shot rings out as Wendy hits him over the head with Brandt’s ashtray. Refusing to stick around and be blamed for Brandt’s murder, Wendy flees for Bangalor airport, with Sarah in tow.
Sarah decides to take the investigation to the Scala offices in the UK, but Wendy reveals that Scala has another office nearby in Tamil Nadu; she found its address on some papers in Brandt’s office. As Wendy buys train tickets, Sarah hits the pay phone to check her voice mail without wasting her mobile’s battery -- and Nat traces the number and calls her back. Surprised when the pay phone rings, Sarah answers with the name of the airport, and is furious when she hears Nat on the other end; if someone is listening in on their calls then Sarah’s just revealed her location. Nat is just as angry with Sarah for keeping her friends in the dark, and reveals what happened to Josh because of it; as far as Nat is concerned, Sarah’s too busy looking for imaginary pursuers to pay attention to what’s really going on. Nat does tell Sarah that Wendy was made redundant by Planet 3 two weeks ago, which is presumably why she’s so desperate for a scoop. Sarah tells Nat to look for a connection between the brucella bacteria tested in Operation Halter and something called the Parambikulam-Aliyar project -- but hangs up when Nat again advises her to stop being so paranoid.
Irritated, Nat nevertheless does as Sarah asks, and when she shows Josh pictures of Scala’s four full-time employees he recognises two of them immediately -- not the CEO nor the chief scientist, Joseph Brandt, but the head of security, Philip Harris, and the financial director, Bandaru Chakravarti. Harris is the man who tried to kill Josh and Ellie Martin with sarin gas, and Chakravarti is one of the two men who robbed Sarah’s flat and put Josh in hospital. Despite Sarah’s refusal to give out her phone number, Natalie will have to track her down again to warn her that she and Wendy are being set up. Josh checks himself out of hospital and buys a plane ticket to India, overcoming his fear of flying for this emergency and taking along Sarah’s special briefcase as a precaution. Meanwhile, Natalie continues to research the four Scala employees, and learns that they were all members of the same scientific research centre in the 1980s, many of whom went to prison for breaches of the Official Secrets Act.
Wendy and Sarah catch the train to Coimbature; unfortunately, all of Wendy’s notes about Scala are still on the Planet 3 server and thus inaccessible due to her redundancy. However, she still has her journalist’s ID, which she can use to get a meeting with the CEO. Sarah is reconsidering the way she’s treated her friends, but Wendy doesn’t believe that investigative journalists can ever truly have friends. Everyone has secrets they don’t want revealed; hasn’t Sarah ever wondered what happened to the people she’s written stories about in the past?
Sarah and Wendy reach their destination and take a taxi to the Scala offices, passing a river and reservoir which Wendy identifies as part of the Parambikulam-Aliyar project, a series of dams and reservoirs used for generating power, irrigation, and drinking water. The taxi drops them off at the Scala offices, where Wendy creates a distraction at the gate while Sarah slips away for a look around the laboratories. She manages to access a computer terminal, and what she learns is horrifying. Natalie then contacts her, but before she can deliver her warning Sarah passes on a warning of her own -- the employees of Scala are planning to release brucella into the Parambikulam-Aliyar project, poisoning the land and killing millions. Natalie tries to warn Sarah about the company’s CEO, but the call is interrupted when Sarah is captured by Scala’s financial director, Bandaru Chakravarti -- the “taxi driver” who dropped her off at Heathrow and subsequently broke into her house.
Unfortunately, Sarah was unable to provide Natalie with details about the forthcoming terrorist attack, and Natalie realises that she’ll never be able to persuade the Indian government to shut down the entire Parambikulam-Aliyar system without providing specific proof of her claims. Searching for further evidence, she hacks into the Planet 3 server to access Wendy’s personal files, but she can’t find any information on Scala -- until she speaks to Josh, and a miscommunication over the phone gives her an idea. Instead of checking Wendy’s personal files, she checks her personnel files -- and finds something very interesting indeed.
Sarah spends a day locked up in the Scala building, but eventually Chakravarti and Harris come to take her to the CEO’s office. There, she is shocked to that Wendy is in charge of them -- but she’s even more shocked when the CEO walks in and is revealed to be her old nemesis Hilda Winters. Wendy’s real last name is not Jennings, but Jellicoe; she’s a relative, either niece or daughter, of the man who went down for murder while Miss Winters got only 15 years in jail. Harris was a member of the SRS as well, but he remained on the outside and has spent the last couple of decades setting up cover operations on the outside. Winters is behind the collapse of Sarah’s journalism career, but revenge is only an amusing sideline -- as ever, her plans are much more ambitious...
Sarah’s mobile phone rings, and Winters allows her to answer the call, which is from Josh. He and Nat are concerned about Sarah, but Sarah tells him that the less things Nat worries about, the better. Josh becomes suspicious, but Winters takes away the phone, the call having served its purpose. When Chakravarti raided Sarah’s apartment he took the electronic equipment which Sarah had mentioned to Sarah, and with her usual disregard for the “personality” of mechanical objects, Winters had Sarah’s “pet” dismantled and analysed. With the technology thus acquired, she has constructed an electronic voicebox with which Wendy can imitate Nat’s voice perfectly and leak information to the press regarding Sarah’s “true” agenda. Chakravarti also planted notes in Sarah’s apartment, both paper and electronic, apparently proving that Sarah herself intends to release the brucella virus into the Parambikulam-Aliyar project, creating a false story about Scala in order to restart her career. To her horror, Sarah discovers that Brandt is still alive and a part of the project; his death was staged, all to lure Sarah her to act as a scapegoat for the terrorist attack which will soon kill millions.
Winters, Brandt and Harris take one car to the dam while Chakravarti, Wendy and Sarah take the second. The doors and windows are sealed, and Wendy puts away her gun, convinced that Sarah can’t escape. Gloating, she plays Sarah a recording of the phone conversation she’s just had with Josh, which continued after Winters disconnected the real Sarah. Sarah listens in horror as someone speaking with Sarah’s own voice tells Josh that Scala has decided to cancel the project -- and that she’s decided to release the virus herself in order to expose them, rather than let them hide away and start up somewhere else. Josh protests, but Sarah’s voice tells him that the less reasons he offers up, the faster this will all be over.
Furious, Sarah attacks the distracted Wendy, trying to force Chakravarti to pull over -- and when he refuses, she sets off her rape alarm, just as she’d threatened to do on the drive to Heathrow. Chakravarti loses control and drives off the road, and Wendy’s legs are trapped when the car crashes into the river. Wendy passes Sarah the gun so she can shoot out the windows, but Sarah can’t get Wendy out of the car and must swim to safety as the car sinks, taking Wendy down with it. Sarah abandons the gun as she swims to shore, but Chakravarti recovers the gun and confronts her -- but at the last moment Josh arrives and shoots him instead, with the gun which he acquired in Romania and smuggled into India in Sarah’s special briefcase. He’s been following them in a hire car ever since they left Scala, having realised that something was wrong when Sarah misused the word “less” rather than “fewer” during their phone conversation.
As Josh recovers from the shock of having shot and killed someone, the other car catches up and tries to run them down, but Josh shoots at the tires, forcing them to flee. He assures Sarah that the Parambikulam-Aliyar project is safe; Nat tracked down a known Tamil Tiger code phrase and alerted the Indian government to expect a terrorist attack, and the dams and reservoirs are all under a tight security clampdown. Natalie has also passed on word about Winters’ past to the UK government, ensuring that Scala will lose its government contracts. Sarah realises that she’s been sadly neglecting her friends, and promises to do better for them in the future. But she’s certain that Winters will give up her plans for the Parambikulam-Aliyar project, thus evading capture -- and now Winters has the technology to carry on her vendetta. This battle has been won, and the enemy has been revealed, but Sarah and her friends are not safe yet...