While a deadly hacker turns Britain upside down, Danny decides whether to reveal all to Will, MI5 hunts the source down to an Islamic mosque with the help of MI5's best computer programmers. But things get suspicious when Ruth, close onto the tail of the hacker, goes missing and so does a member of the special team...

It's Fiona's birthday, and she's not going to forget it! While inspecting a possible Islamic terrorist safe house, they are kidnapped. With the threat of his son's, his wife's and Danny's life, Adam must choose who won't live to see another day, Fiona or Danny? The prime minister's life is in danger. Will MI5 give into the kidnappers demands? But then to everybody's surprise... Danny makes the ultimate sacrifice.