An unnamed Middle Eastern country is preparing to invade Europe. A small group of bright minds, trying to convince the European governments to arm for the coming war, find their members killed of one after the other. Next on the list is Tweed, who gathers his team of agents to find the killers, a group of mysterious women, led by the son of the Head of State of the unnamed Middle Eastern country.
Their journey takes them from England to Vienna, Zürich and Slovakia. As usual in Forbes's books, much time is spent in hotels and there's plenty of dialog, and Tweed and his team owe as much of their successes to luck as to skill. But there's also a fair share of action and despite its flaws (stilted dialog and plenty of clichés, and the pace could have been somewhat faster), "The Sisterhood" is an enjoyable, but not great, book.