MI-5 is alarmed when the death of a young primary school teacher brings the number of paracetamol-related fatalities to 9, with 11 more victims in a serious condition listed across Britain. It transpires that different brands of pills have been laced with menazorphine, which would alter its effect to like drinking acid. Someone on the outside has hacked into the manufacturer's computer systems and deliberately caused this lethal cocktail to occur. Ruth, with the help of Andrew (an old colleague and analyst from the National High Tech Crime Unit), investigate the possibility that Islamic terrorists are behind the threat. Together they try to trace the hackers behind the chaos that is now spreading across the country. Bank balances are being wiped, traffic lights are out of synch, everywhere there is mayhem and tragedy. Devastated and bitter at losing Zoe, Danny is obstructive on the operation and nasty to Ruth - until she goes missing, just as she was about to uncover the hacker's identity. Working closely with the team, he deduces that the hacker is Andrew (an insider) and that he?s holding Ruth. His demand? The valuable G&J key, a tool which controls the world's computers. Adam negotiates a ransom deal and Danny races to Ruth's rescue. Now Danny tells Will where Zoe is, and the lovers are reunited.