When sixteen-year-old Tessa Gray crosses the ocean to find her brother, her destination is England, the time is the reign of Queen Victoria, and something terrifying is waiting for her in London's Downworld, where vampires, warlocks and other supernatural folk stalk the gaslit streets. Only the Shadowhunters, warriors dedicated to ridding the world of demons, keep order amidst the chaos.

Kidnapped by the mysterious Dark Sisters, members of a secret organization called The Pandemonium Club, Tessa soon learns that she herself is a Downworlder with a rare ability: the power to transform, at will, into another person. What's more, 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 of the London Institute, who swear to find her brother if she will use her power to help them. She soon finds herself fascinated by--and torn between--two best friends: James, whose fragile beauty hides a deadly secret, and blue-eyed Will, whose caustic wit and volatile moods keep everyone in his life at arm's length...everyone, that is, but Tessa. As their search draws them deep into the heart of an arcane 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.

Amazon Exclusive: A Q&A with Cassandra Clare, Author of Clockwork Angel

A: The Infernal Devices take place in the same universe as The Mortal Instruments, but a hundred and fifty years before the events of the Mortal series. You absolutely don't have to read The Mortal Instruments first; I've gotten very enthusiastic feedback from people who started with Clockwork Angel. However, if you are a fan of the Mortal Instruments, you'll see familiar family names--Lightwood, Wayland--and get to see what the ancestors of the characters you already know were up to in the Victorian age. There is at least one character who crosses over both series: the immortal warlock Magnus Bane. For those familiar with the Mortal books, it should be fun to meet him again; for those who haven't read them, it should be fun to meet him for the first time!

Q: Do you have a favorite character in Clockwork Angel?

A: Like Tessa, I'm torn between Jem and Will! They were both so wonderfully fun to write. Despite having a close brotherly bond, they're really opposites in personality. Will is a character who hides almost everything about himself; Jem is a character who is almost unendingly open and kind. Of course, when either kind of character reaches their breaking point, you have those moments of high drama and intensity that are catnip to writers!

Q: What characteristic or personality trait does Tessa possess that you most admire?

A: She is extremely persistent and unwilling to give up. When she's imprisoned, she doesn't stop trying to escape; she never stops trying learn new information; she never stops looking for her brother. She never fades quietly into the background; she plants her feet and asks questions--and gets answers, often from the unlikeliest of sources.

Q: How much research did you do for Clockwork Angel? What was the most interesting thing that you learned?

A: Starting in January of 2009 I took a six-month period of reading only books written during, or set in, the Victorian era--both fiction and nonfiction. I have an entire bookshelf now dedicated just to Victoriana. I also hired a research assistant who dug through primary source materials to find me letters and diaries written at the time. I was especially keen to find diaries of Americans traveling abroad, since Tessa is an American in London. I wanted to get a sense of what her impression as a foreigner would have been. One of the creepiest things I learned about was Victorian death photos, where they would prop up corpses to seem alive and take photos of them for their loved ones to have as keepsakes.

Q: Which type of character is the most fun for you to write--the hero or the villain?

A: There's a huge appeal to writing both, but there's something special about creating a really good villain. The villain stands outside society. He or she can say or do anything without fear of what the consequences will be for his/her relationships with the other characters. Sometimes the villain is the only one who can speak a vicious or painful truth and get away with it.