The initial shock and revulsion quickly gave way to anger and an intense search for the perpetrators. Atop the list of possible suspects was ISIS, the extreme jihadist group that had terrorized and beheaded its way to an Islamic caliphate stretching from Aleppo nearly to the gates of Baghdad. The group had vowed to attack the West, and its ranks included several hundred residents of the United Kingdom who had retained their precious British passports. Surely, declared the television experts, ISIS had both the motive and the capability to strike in the heart of London. But an ISIS spokesman denied the group had been involved, as did several other elements in the global Islamic conglomerate of death known as al-Qaeda. A remote Palestinian faction did claim responsibility, as did something called the Martyrs of the Two Holy Mosques. Neither claim was taken seriously.

The one person who could answer the question of responsibility was the woman who had delivered the bomb to its target: Anna Huber, thirty-two years of age, German citizen, last known address Lessingstrasse 11, Frankfurt. But forty-eight hours after the attack, her whereabouts remained a mystery. Attempts to track her movements electronically proved useless. CCTV briefly showed her walking along Brompton Road toward Knightsbridge. But after the detonation, as smoke, debris, and panicked crowds poured into the street, the cameras lost sight of her. No one named Anna Huber had left the country via plane or rail; no one named Anna Huber had crossed another European frontier. Units of the German Bundespolizei raided her apartment and found four uninhabited rooms containing no trace of the person who might have once lived there. Neighbors described her as quiet and introspective. One said she was an international aid worker who spent a great deal of time in Africa. Another said she did something in the travel industry. Or was it journalism?

Responsibility for protecting the British homeland from terrorist attack fell primarily to MI5 and the Joint Terrorism Analysis Center. As a result, public and political anger over the Brompton Road bombing was directed largely at Amanda Wallace. The word embattled began to appear before her name in print or whenever it was mentioned on television or radio. Unnamed sources at the Met complained that the Security Service had been “less than forthcoming” with intelligence related to the attack. One senior investigator likened the flow of information from Thames House to Scotland Yard to the advance of a glacier. Later, he clarified his statement, calling cooperation between the two organizations “nonexistent.”