The terror suspect is released without charge by the police and disappears underground, only to resurface and kill two surveillance officers before trying to shoot down a commercial aircraft.
It's only a fictional plotline from a popular British television serial, but it neatly encapsulates a very real debate in a country struggling to come up with a plan to thwart terrorism.
Four months after the July 7 London terror attacks, the midsummer unity so in evidence after the quadruple bombings has curdled. Now the country is divided as to whether muscular new police powers are the best way to defeat terrorists, or a counterproductive move that will encourage disgruntled Muslims to join the militant camp.
On one side of the debate stand Prime Minister Tony Blair, senior police officers, and a sizable chunk of public opinion - all backing government attempts to push through legislation that would, among other things, give police far more than the current 14 days to detain suspects without charges.
On the other side of the argument are numerous members of Parliament (MPs), lawyers, and libertarians aghast at the implications for civil liberties of the government's Terrorism Bill, which has echoes of the US Patriot Act (though the accent is more on interrogation than surveillance).
The controversial legislation is enduring a stormy passage through Parliament, prompting many to wonder if legislating is the best way to confront terror. Last week, MPs in the House of Commons rejected a clause that would have allowed police to detain suspects for 90 days without charge, voting instead for a 28-day limit. It was Blair's first defeat as prime minister on a whipped vote, in which party members are required under threat of discipline to vote the party line. While the 90-day measure was struck down, the Terrorism Bill could still become law if it clears the House of Lords.
"Dogs bark, babies cry, politicians legislate," says Paul Flynn, one of the 49 Labour MPs who voted against the 90-day proposition. "But it's just not appropriate to tackle terrorism with laws like this. Police always want more powers, but we've seen dreadful misuse of police power in the past."
So controversial is the issue that it even divides heroes and victims of 7/7. One victim, John Tulloch, said last week that he objected to a British newspaper juxtaposing his stricken image with the text "Tell Tony He's Right," strongly implying that Mr. Tulloch supported Blair's new laws. Another man, Paul Dadge, whose act of heroism in rescuing a victim made him front-page news, said he was "dumbfounded" by MPs rejection of the 90-day provision.
But Bob Marshall-Andrews, another Labour MP who opposes the legislation, says that sacrificing cherished civil liberties for the faint promise of greater security would play into terrorists' hands.
"If you take action to remove really very fundamental civil liberties, you are in very grave danger of creating the problems you are trying to solve," he says. "If people are locked up for long periods without trial, you are creating the kind of state the terrorists want us to."
The police argument for the unprecedented suspension of habeas corpus - a right enshrined in law since 1679 - is that the rules of the game have changed since the days of the IRA and their coded alerts. According to London's police chief, Sir Ian Blair, there are people in Britain "plotting mass atrocity without warning." Sophisticated technology and international links make it harder for police to penetrate the treacherous plots.
Police argue that they need more time than ever before to sift data, decrypt hard drives, check cellphone records, and chase international leads before they can be sure that a suspect in detention is dangerous and chargeable, or harmless. They note that it took two months to scour a rubbish dump in northern England for evidence left by the 7/7 villains.
Top antiterror officer Andy Hayman said last week he was concerned that police investigations could be "frustrated by the guillotine of time." Police say they have thwarted two attacks since 7/7. But they believe their hands will be tied unless they have the additional detention time.
"We are not looking for legislation to hold people for up to three months simply because it is an easy option," Mr. Hayman said. "It is absolutely vital. To prevent further attacks we must have it."
Yet counterterrorism experts question whether the solution is appropriate to the police's needs. Bob Ayers, a security expert at London's Chatham House think tank, says that if the problem is technology, then the solution may be to invest in better analytical capabilities.
"Rather than elongate the detention period, why not invest in the capability to provide timely quality forensic investigation?" he says. "The reason it takes so long is that they do not have the requisite number of highly skilled technicians and the technology that allows this forensic investigation to be performed.
"It's not proper to make citizens suffer incarceration because we haven't equipped police to deal with this 21st-century problem," he adds.
Mr. Ayers says that no amount of precharge detention would have prevented 7/7, as none of the perpetrators had been in police custody before. And he notes that in the case of the attempted bombings two weeks later, indictments were swiftly brought - well within the two-week period currently permitted.
"It doesn't take three months to say 'here's a CCTV picture of the man with the bomb - we've got him,' " he says, referring to the closed-circuit TV systems widely used for surveillance in Britain.