16 year-old Tessa is all alone in the world. Her parents died when she was 3, her brother, Nate, moved to London and her Aunt Harriet who raised her has just died as well. Nate sent her a ticket for a ship to London so that she could join him, but he didn't meet her at the dock. A couple of old ladies - the Dark Sisters - did, they had a note from Nate telling her to trust the ladies, so she went with them, but no sooner did they arrive at their house, than they imprisoned her and demanded that she change for them. She had no idea what they were talking about, but soon they were able to train her to change into other people, if she had been able to hold something of that person's. She doesn't like or trust the Dark Sisters, or their maid Miranda, something's just not right about her, but Tessa can't quite put her finger on it. But she has no choice, because the sisters keep telling her that if she doesn't do exactly as they say, Nate will die. As soon as the Dark Sisters start talking about having her marry someone called The Magister, she knows she has to escape, regardless of the penalties for Nate. She is rescued by Will Herondale and some others, but she has no idea that they aren't human, and neither is she! I really enjoyed this book, I thought that it may be a bit too dark, but while it was on the dark side, it was really a fun, mysterious read. I do wish that more authors would learn not to add a bunch of swear words. This wasn't terrible that way, but it wasn't squeaky clean either.