Philip Pullman's The Butterfly Tattoo

"Chris Marshall met the girl he was going to kill on a warm night in early June, when one of the colleges in Oxford was holding its summer ball." A chance meeting with Jenny at an Oxford party leaves seventeen-year-old Chris with hope for a summer romance - and no premonition of trouble. Busy with his job and soon in love with Jenny, whose cheerful surface belies the dark uncertainty of her past, Chris misses all the signs of danger. Before he knows it, he's caught in the sinister web of a criminal whose desire for revenge crushes those who stand in his way.