Magic is dangerous -- but love is more dangerous still.

WHEN SIXTEEN-YEAR-OLD TESSA GRAY crosses the ocean to find her brother in Victorian England, something terrifying is waiting for her in London's Downworld. Kidnapped by the mysterious Dark Sisters, who are members of a secret organization called the Pandemonium Club, Tessa soon learns that she has the power to transform at will into another person. The Magister, the shadowy figure who runs the Club, will stop at nothing to claim Tessa's power for his own. Friendless and hunted, Tessa takes refuge with the Shadowhunters, warriors dedicated to ridding the world of demons. She soon finds herself fascinated by -- arid torn between -- two best friends: James, whose fragile beauty hides a deadly secret, and Will, whose volatile moods keep everyone at arm's length. As their search draws them deep into a plot that threatens to destroy the Shadowhunters, Tessa realizes that she may need to choose between saving her brother and helping her new friends save the world ... and that love may be the most dangerous magic of all.