The Judas Goat
Robert B. Parker
Quercus 
<p>Private detective Spenser has travelled to London in search of the bombers who attacked his client's family. His job is to catch them. Or kill them. His client isn't choosy.</p><p>But there are nine killers to one Spenser - long odds. Hawk helps balance the equation. The rest depends on a wild plan. Spenser will get one of the terrorists to play Judas Goat - to lead him to the others. Trouble is, he hasn't counted on her being blond, beautiful and very dangerous.</p>